Not a stat topic, but still good info that I don't think should be wasted.
From mc
This contains a summary of the growth formulae, and how they work in level-up-down. Following which it contains the percentage increases of level up/down of various classes at a few different levels. Finally there is an Appendix for the duelling metagame with Maxed Stats FFT characters (since, really, what else are you going to do with all those stats?) Not sure if this topic belongs in the unranked games (FFT is ranked...but level-up-down FFT is not...barring really, really weird interpretations I guess...).
[size=18]The Stats[/size]
The idea of Level Up Down is to level up in a class with good stats, and then level down in a class with bad stats, and repeat this process a few times to max out your stats. There are five stats that change when you gain or lose levels in FFT: HP, MP, Speed, PA, MA. HP and MP have an in-battle cap of 999. PA and MA have an in-battle cap of 99. Speed has an in-battle cap of 50. In addition, there is an internally stored number which will not go higher than 16777215 (which translates into 1024 of a stat given a 100 multiplier). This means that classes with lower multipliers on HP/MP will not be able to cap them (for instance, Ninja tops out at 716 base HP, 511 base MP). All other stats can easily pass their in-battle caps of 50-99, given enough patience.
[size=18]Up-Down Formulae[/size]
From the BMG, the bonus you get from levelling up is...
bonus = [current_RX / (C + Lv)]
(Where Lv is the level you are levelling from).
And the amount you lose from levelling down is...
decrement = [current_RX / (Lv + C)]
(Where Lv is the level you are levelling down to).
It's actually easier to think of these in multiplicative terms
new_RX = current_RX * (C+Lv+1)/(C+Lv)
Over, say, three levels this will become...
(C+Lv+3)/(C+Lv+2) * (C+Lv+2)/(C+Lv+1) * (C+Lv+1)/(C+Lv)
= (C+Lv+3)/(C+Lv)
So in general if you are levelling from Lv_low to Lv_high it's...
new_RX = current_RX * (C+Lv_high)/(C+Lv_low)
The idea of level-up-down is to gain stats by levelling up in a class with low C-value, and levelling down in a class with high C-value. However note that if the C-values are equal, you actually lose stats (at a very slow rate):
current_RX * (C+Lv+1)/(C+Lv) * (C+Lv-1)/(C+Lv)
= current_RX * (1 - 1/(C+Lv)^2)
This is why you use different C values.
(C_up+Lv+1)/(C_up+Lv) * (C_down+Lv-1)/(C_down+Lv)
=1 + (C_down - C_up - 1)/((C_Up+Lv)*(C_down+Lv))
In short, the percentage you gain is (roughly) equal to the difference between the C-values, divided by the level squared. In other words, it is much, much more effective to level-up-down at lower levels. This quadratic decay has nothing to do with FFT growth being quadratic--FFT growth is linear. No, it has to do with you're getting a linear bonus on the way up, AND a linear bonus on the way down, which multiply for a quadratic bonus. (It is very important to think about the gain from level up down in terms of the percentage or ratio at which you're increasing a stat, because the overall effect is exponential).
When gaining N levels we get....
(C_up+Lv+N)/(C_up+Lv) * (C_down+Lv-1)/(C_down+Lv+N-1)
= N(C_down+Lv-1)/((C_up+Lv)*(C_down+Lv+N-1)) - N(C_up+Lv)/((C_up+Lv)*(C_down+Lv+N-1)) + 1
=1 + N*(C_down-C_up-1)/((C_up+Lv)*(C_down+Lv+N-1))
Very similar to the previous equation, just we multiply by the number of levels we go up...but also divide by a somewhat larger number. In particular, as N goes to infinity, this becomes....
=1 + (C_down-C_up-1)/(C_up+Lv)
Which means if we levelled up to infinity, and then levelled back down to zero, our stats would not be maxed out (even though they would be maxed at infinity). Basically, above a certain level, the fact that it's (C+Lv) will cause the Lv to drown out the C, meaning there's no real difference between one growth and another, so going up in one growth and down in another will have no particularly noticeable effect.
[size=18]Up-Down Charts[/size]
HP: up Mime (6) down: Bard/Dancer (20)
1-11: 61.90% bonus (100% efficient compared to low levels)
11-21: 19.12% bonus (36% efficient compared to low levels)
21-31: 9.63% bonus (19% efficient compared to low levels)
31-41: 5.86% bonus (12% efficient compared to low levels)
41-51: 3.95% bonus (8% efficient compared to low levels)
51-61: 2.85% bonus (6% efficient compared to low levels)
61-71: 2.16% bonus (4% efficient compared to low levels)
71-81: 1.69% bonus (3% efficient compared to low levels)
81-91: 1.36% bonus (3% efficient compared to low levels)
91-99: 0.91% bonus (2% efficient compared to low levels)
HP: up Ninja (12) down: Bard/Dancer (20)
1-11: 17.95% bonus (100% efficient compared to low levels)
11-21: 7.61% bonus (44% efficient compared to low levels)
21-31: 4.24% bonus (25% efficient compared to low levels)
31-41: 2.71% bonus (16% efficient compared to low levels)
41-51: 1.89% bonus (11% efficient compared to low levels)
51-61: 1.39% bonus (8% efficient compared to low levels)
61-71: 1.07% bonus (6% efficient compared to low levels)
71-81: 0.84% bonus (5% efficient compared to low levels)
81-91: 0.68% bonus (4% efficient compared to low levels)
91-99: 0.46% bonus (3% efficient compared to low levels)
MP loss: up Mime (30) down: Bard/Dancer (20)
1-11: -11.83% bonus (100% efficient compared to low levels)
11-21: -6.71% bonus (55% efficient compared to low levels)
21-31: -4.31% bonus (35% efficient compared to low levels)
31-41: -3.01% bonus (24% efficient compared to low levels)
41-51: -2.21% bonus (18% efficient compared to low levels)
51-61: -1.70% bonus (14% efficient compared to low levels)
61-71: -1.34% bonus (11% efficient compared to low levels)
71-81: -1.09% bonus (9% efficient compared to low levels)
81-91: -0.90% bonus (7% efficient compared to low levels)
91-99: -0.62% bonus (6% efficient compared to low levels)
MP: up Ninja (13) down Bard/Dancer (20)
1-11: 14.29% bonus (100% efficient compared to low levels)
11-21: 6.25% bonus (45% efficient compared to low levels)
21-31: 3.53% bonus (26% efficient compared to low levels)
31-41: 2.27% bonus (17% efficient compared to low levels)
41-51: 1.59% bonus (12% efficient compared to low levels)
51-61: 1.17% bonus (9% efficient compared to low levels)
61-71: 0.90% bonus (7% efficient compared to low levels)
71-81: 0.71% bonus (5% efficient compared to low levels)
81-91: 0.58% bonus (4% efficient compared to low levels)
91-99: 0.39% bonus (4% efficient compared to low levels)
MP: up Summoner (8) down Bard/Dancer (20)
1-11: 40.74% bonus (100% efficient compared to low levels)
11-21: 14.47% bonus (40% efficient compared to low levels)
21-31: 7.59% bonus (21% efficient compared to low levels)
31-41: 4.70% bonus (13% efficient compared to low levels)
41-51: 3.21% bonus (9% efficient compared to low levels)
51-61: 2.33% bonus (7% efficient compared to low levels)
61-71: 1.77% bonus (5% efficient compared to low levels)
71-81: 1.39% bonus (4% efficient compared to low levels)
81-91: 1.12% bonus (3% efficient compared to low levels)
91-99: 0.75% bonus (3% efficient compared to low levels)
Speed: up Ninja (80) down: anything else (100)
1-11: 2.13% bonus (100% efficient compared to low levels)
11-21: 1.74% bonus (82% efficient compared to low levels)
21-31: 1.45% bonus (68% efficient compared to low levels)
31-41: 1.22% bonus (58% efficient compared to low levels)
41-51: 1.05% bonus (49% efficient compared to low levels)
51-61: 0.91% bonus (43% efficient compared to low levels)
61-71: 0.79% bonus (37% efficient compared to low levels)
71-81: 0.70% bonus (33% efficient compared to low levels)
81-91: 0.62% bonus (29% efficient compared to low levels)
91-99: 0.45% bonus (27% efficient compared to low levels)
Speed Loss: up not Ninja (100) down not Ninja(100)
1-11: -0.09% bonus (100% efficient compared to low levels)
11-21: -0.08% bonus (83% efficient compared to low levels)
21-31: -0.06% bonus (71% efficient compared to low levels)
31-41: -0.05% bonus (61% efficient compared to low levels)
41-51: -0.05% bonus (53% efficient compared to low levels)
51-61: -0.04% bonus (46% efficient compared to low levels)
61-71: -0.04% bonus (41% efficient compared to low levels)
71-81: -0.03% bonus (36% efficient compared to low levels)
81-91: -0.03% bonus (32% efficient compared to low levels)
91-99: -0.02% bonus (29% efficient compared to low levels)
PA: up Mime (35) down: Bard (80)
1-11: 13.58% bonus (100% efficient compared to low levels)
11-21: 9.57% bonus (72% efficient compared to low levels)
21-31: 7.14% bonus (54% efficient compared to low levels)
31-41: 5.56% bonus (42% efficient compared to low levels)
41-51: 4.45% bonus (34% efficient compared to low levels)
51-61: 3.65% bonus (28% efficient compared to low levels)
61-71: 3.06% bonus (24% efficient compared to low levels)
71-81: 2.59% bonus (20% efficient compared to low levels)
81-91: 2.23% bonus (17% efficient compared to low levels)
91-99: 1.57% bonus (15% efficient compared to low levels)
PA: up Ninja (43) down: Bard (80)
1-11: 9.09% bonus (100% efficient compared to low levels)
11-21: 6.67% bonus (74% efficient compared to low levels)
21-31: 5.11% bonus (57% efficient compared to low levels)
31-41: 4.05% bonus (46% efficient compared to low levels)
41-51: 3.30% bonus (37% efficient compared to low levels)
51-61: 2.74% bonus (31% efficient compared to low levels)
61-71: 2.31% bonus (26% efficient compared to low levels)
71-81: 1.97% bonus (22% efficient compared to low levels)
81-91: 1.71% bonus (19% efficient compared to low levels)
91-99: 1.21% bonus (17% efficient compared to low levels)
PA (poor man's style) up Knight (40), down Chemist (75)
1-11: 9.76% bonus (100% efficient compared to low levels)
11-21: 7.02% bonus (73% efficient compared to low levels)
21-31: 5.31% bonus (56% efficient compared to low levels)
31-41: 4.16% bonus (44% efficient compared to low levels)
41-51: 3.36% bonus (35% efficient compared to low levels)
51-61: 2.77% bonus (29% efficient compared to low levels)
61-71: 2.32% bonus (25% efficient compared to low levels)
71-81: 1.98% bonus (21% efficient compared to low levels)
81-91: 1.70% bonus (18% efficient compared to low levels)
91-99: 1.20% bonus (16% efficient compared to low levels)
PA up Ninja (43), down Dancer (50)
1-11: 2.27% bonus (100% efficient compared to low levels)
11-21: 1.59% bonus (70% efficient compared to low levels)
21-31: 1.17% bonus (52% efficient compared to low levels)
31-41: 0.90% bonus (40% efficient compared to low levels)
41-51: 0.71% bonus (32% efficient compared to low levels)
51-61: 0.58% bonus (26% efficient compared to low levels)
61-71: 0.48% bonus (21% efficient compared to low levels)
71-81: 0.40% bonus (18% efficient compared to low levels)
81-91: 0.35% bonus (15% efficient compared to low levels)
91-99: 0.24% bonus (13% efficient compared to low levels)
MA: up Mime (40) down: anything else (50)
1-11: 3.66% bonus (100% efficient compared to low levels)
11-21: 2.52% bonus (69% efficient compared to low levels)
21-31: 1.84% bonus (51% efficient compared to low levels)
31-41: 1.41% bonus (39% efficient compared to low levels)
41-51: 1.11% bonus (31% efficient compared to low levels)
51-61: 0.90% bonus (25% efficient compared to low levels)
61-71: 0.74% bonus (21% efficient compared to low levels)
71-81: 0.62% bonus (17% efficient compared to low levels)
81-91: 0.53% bonus (15% efficient compared to low levels)
91-99: 0.37% bonus (13% efficient compared to low levels)
MA loss: up anything but Mime (50) down: anything but Mime (50)
1-11: -0.33% bonus (100% efficient compared to low levels)
11-21: -0.23% bonus (72% efficient compared to low levels)
21-31: -0.18% bonus (54% efficient compared to low levels)
31-41: -0.14% bonus (42% efficient compared to low levels)
41-51: -0.11% bonus (34% efficient compared to low levels)
51-61: -0.09% bonus (28% efficient compared to low levels)
61-71: -0.08% bonus (23% efficient compared to low levels)
71-81: -0.06% bonus (19% efficient compared to low levels)
81-91: -0.05% bonus (17% efficient compared to low levels)
91-99: -0.04% bonus (15% efficient compared to low levels)
[size=18]In Practice[/size]
If you want an uber character quickly, get yourself some PA.
If you're looking to max everything, there are basically three problem stats: Speed, MA, and MP. Speed can only be raised by Ninja, MA can only be raised by Mime, and Mime kills MP.
If you're looking for a maxed stats female Ninja... (see appendix for why you might want this class in particular)
Level 1 maxed stats requires:
57 cycles of 1-20 Ninja, 20-1 Dancer
63 cycles of 1-20 Mime, 20-1 Dancer
14 cycles of 1-20 Summoner, 20-1 Dancer
Level 99 maxed stats requires:
34 cycles of 1-20 Ninja, 20-1 Dancer
42 cycles of 1-20 Mime, 20-1 Dancer
10 cycles of 1-20 Summoner, 20-1 Dancer
While MA does grow faster than Speed with 1-20 cycles, it also has a longer way to increase. (MA needs to double 3-5 times; Speed needs to double 1.5-3 times). MP needs to double 4 times/7 times depending on level 1/level 99, but it's much faster to double (nearly every Summoner cycle).
Now, realistically you'll probably do shorter cycles with Summoners (1-10, say) and longer cycles with Ninjas (1-30), as MP growth is very front loaded, and Speed growth is not very front loaded, but this gives a rough idea.