On another note, 20" isn't very deep. How wide is it?
Cabinets can make alternative cages, but with these smaller cages, bunnies need much more out-of-cage time.
I'm going to attach another picture of a cabinet-type cage I made (from a kitchen oven cabinet). But with this size cage, I keep the cage door open all day long. It is opened first thing in the morning and not closed until about 11pm.