@hoosiercheetah
PS:
If you are good a wiring, and have some heavy, suitable wiring to work with, I think I'd try the cinder block thing.
I have some bricks and blocks around here that I've built up where I have pyrex bread pans sitting in them with the rim/handles of the bread pan sitting on the brick edges to raise it up off the floor. (I'll get a photo later.) That would be an ideal setup to use and put a heat source under it since it can be completely lined with bricks/block.
Only thing w/my setup is that it would always have light on under there showing through the glass. But if you take the in at night and turn the light off, it would work beautifully.... (I have LOTs of bricks and patio blocks around here in the "storehouse".
Now that I'm going to have more indoor room, I might just consider doing that myself if I can find some good way to wire it that it's safe.....
(I just didn't have enough room indoors to make that work in the hen shed.