I'm putting the finishing touches on a new hollow core door rack using the biggest underbed (i.e. low profile) boxes I've seen. I got them at Sam's club per a post by Sean at http://www.ballpythonmorphs.com . They are about 37" X 22" X 6". Lots of floor space for a good-sized ball or even a young boa but without the height to make them feel exposed. These boxes look much larger than the narrower 16" - 18" wide by 34" long ones that you see at Target and the like for about the same price.

My problem is that I'm trying to get by with one strip of 11" heat tape down the back in a very cool basement. The hollow core door construction is a pretty good insulator but I ran out of doors and used fiberboard on the back. I'm going to insulate the back and retro fit each shelf with metal flashing on the inside back and coming out a bit to try to spread the heat out more. I wish I had used a couple big sheets of metal to sandwich the heat tape before I put the back on. It just seems like it’s not spreading out across the entire 24” width of the rack and too much heat is going out the back through the fiber board. Also, 3 foot to the front is just too far to pull the heat forward in my cold basement so hopefully the metal around the back1/3 of the box will spread the heat out more and make better use of it and the insulation on the back outside will keep it headed in the right direction (into the box).