You could throw a hide in there to offer reduced space.

4" heat tape from Reptile Basics is 6 watts per foot and the 12 " is 23 watts. The commercial racks come with 4" which I think is safer if the t-stat fails in the "on" position. I only use the larger heat tape for back heat, not belly heat.

I used to use aspen sani-chips but switched to either paper towels or heavy cage/tub liners. I clean more often but it's easier. Try both ways and decide.