Ok, time to do pointless Math because i'm bored.
Let's take, for this, a Gardevoir of XL Size (this increases the base height of 40%). A Gardevoir is normally 160 cm tall, so now we have a 224 cm tall specimen.
Now, let's pretend that his specific Gardevoir can learn the move Growth. This move increases Attack and Special Attack by one Stage, and for the sake of this test we'll consider her Height as a stat, which is also affected by the move.
Stat raise in battle works that, for each stage the specific stat is increased, a multiplier gets added to the base value. This multiplier is "1.5+Stage/2". A stat can reach a maximum of Stage 6.
Growth, as we said, increases Atk, SpA and Height by one Stage for each use. Let's say Gardevoir uses Growth 6 times then, this would cause her base Height to be multiplied by 1.5+6/2 = 4
224*4 and we obtain a humongous 896 cm tall Gardevoir. That's quite large.
haha
