I have a UTH stuck to the bottom of my tank. My question is what should the temp be set at if there is substrate on top of the heat mat? I have a temp probe placed on top of the glass beneath the substrate that usually reads about 100 degrees, but if I feel the substrate with my hand its barely warm. Should I turn up the dimmer to heat the substrate better? I don't want to burn the snake.

There is about half an inch of repti bark over the heat mat. Should I use less substrate over the mat or add more repti bark and crank up the rheostat? I've seen the snake burrow or push away some substrate to get down to the glass.

I don't have a temp gun ATM, but plan on investing in one.