Tried electrical tape, it just kinda disintegrates. And I'm taping it from the outside, the pad is staying, its just not staying very flush, I know its probably mainly caused from the thermostat probe but I just wasn't sure if there was a better way to do it. Due to the incoming cooler weather I'm trying to really get his tank set as much as I can, was sure if foam pad would help with keeping the UTH more flush as well as providing a bit of insulation. I love my Florida weather but in the winter even Floridians have to watch the temps in the tank to make sure they don't drop. (First winter with a reptile)