Since people who work with rabbits seem to end up in this forum section. I thought this might be a good place to let you know that Jim Gerrish has completed his article on making his Chocolate Bunny Box from hardboard and duct tape (on my site). In this project, he actually uses a bit more than that- some wooden molding for box reinforcement against the "kickers" and the "agitated". The same box can double as a "regular" bunny box, or the Letter From Santa box, or a balloon to bunny box, and so on.

Since you make it yourself, you can design it to any size rabbit, and even build new boxes as the rabbit grows (they only cost about $10 to build and take a week-end of your time ... mostly spent sipping martinis and waiting for the glue or paint to dry).