I have the UTH covering about 1/3 of the bottom. When I set it up, I did adjust the thermostat based on the temperature of the glass (with a temp gun) directly on top of the UTH. I also use the temp gun for the surface of the substrate, as well as an accurite for ambients. I'm concerned however, especially since he is a burrowing snake, how do I determine the accurate temp of the glass on top of the UTH if the temp gun won't read it accurately?