Balls are usually better off with some sort of belly heat. It helps with their digestion. A heat lamp or CHE could work, but keeping the humidity up may be a problem.
It may be worth it to see if you can find a way to get some sort of belly heat in there. Perhaps have a layer of glass on the inside on the bottom with the heat source sandwiched between the wood and the glass? I dunno, that may be asking for a fire hazard
If you go with the CHE on the side, be sure there is some sort of mesh/cover over it. Even if it's up off the ground, BP's still like to climb sometime, and I would hate to see your lil guy get burned!
Either way you should post pictures when you are done!