Hi there!~
I have 3 cages from RBI and they are the 2x3x12 size. I feel that this size will comfortably hold any adult ball. One Helix will run 3 cages. Since they are not arboreal, they require nothing higher than 12 inches. I also have racks from RBI that I am very happy with and one Helix will run about 6 racks. I have mine running 3 racks and I'll also hook another one up soon. I have the 32 qt rack and will get the CB-70 next (for the females that are not in the cages.)
Rich is a great person to deal with and he is very willing to help you if you have any questions or concerns. He sells temp guns, Helix's, and all the other supplies you might need. He'll do belly or back heat (belly for the balls). I feel that the quality of his product and the really good and attentive customer support he gives continues to make him my 'go-to guy' for cages and racks. I guess if I ever needed a really big rack set-up I'd have to drive to N. Carolina and beg him to do a custom for me!!