I am building 2 similar racks right now, only I built mine with 5/8 sanded pine plywood with about 5 coats of polyurethane on it. I built 2 racks for the same problem your running into... I have an adult rack, and a 1/2 hatchling, 1/2 sub adult rack. I will have a thermostat for each though, 1 for adults, 1 for hatchlings, and 1 for sub adult just to make sure Im running at the right temps on each one...