Belly Heat?

I was just reading another thread and someone mentioned belly heat. I use heat lamps and put pieces of slate rock in the cages for my Iggy and Beardys, I heard that helps them digest thier food better. Is this needed for BPs? I have recently cut a hole in the top of Salinas cage and moved the light up and out, I also switched to a red light which she seems to love. She is a lot more active now. Should I put a piece of rock in to help her digest her food a little better?

You need a heating element under the cage to create the belly heat...

My current cage is 22" x 13". can you send me a quote on a piece of flexwatt that will fit that. The flexwatt will go on top of a peice of press board and under a piece of fiberglass, this will be caulked to keep out moisture.