I use shelves instead of a rack for now, but I mix em up. I use the same size UTH and a single thermostat to control my corn and hognose. I also use a similar setup for my boa and one of my bp's. The way it's setup, the bp's warm spot is about 3 degrees higher than the boa's. It seems to work pretty well, and I use a temp gun to double check everything. When I get actual racks, I will do the same thing if I need to.