I got my baby ball in a 40 breeder and he's tiny. Eats great! All and all everything is perfect and the 40 breeder will last him his whole life. If you're worried about humidity I take 2 small dish towels and place them on top of each other wet on each side of my heat lamp which is on the middle of the screen and temps and humidity are 100% PERFECT.

(I also use beaked moss and mist it once a day pretty good.)