Don't get the Radiant heat panel unless your room is very warm. They aren't alot better than a heat mat or flexwatt. I have used them and it didn't heat the enclosure anywhere near where i needed. I keep boas and have them in 4x2x16 high enclosures with the che mounted just as you described. I have near perfect temps. Even though I keep the boas in a basement which is usually 60-65 degrees. My warm side is 98 right under the che and the cool side all the way against the farthest wall is 78-80 depending. Your cage may be too tall I have had this problem with some earlier cages I built. If you go with my dimensions you will be good to go. I do have the problem with it heating the ceiling right above the che as well as the cage above it somewhat so I have to run the che on the cage on top down lower than the one on the bottom or I would over heat it. But i have successfully bred my boas in this setup for the past two years two different femals I might add. SO it apparently works very well.