Hello. First post here. We are looking at adopting a pair of Holland Lops. But first I am going to repurpose an old computer hutch that is just storing DVD's and junk. How much space should be between the different levels? I have a small built in one at the top but it is only 29 inches from the main level. I would like to add a level between them but didn't know if there is enough space. The hutch is 20.5 inches deep. Thanks.