rough scale sand boa tank setup questions

In a surprise move very unexpected my roommate got an adult female Rough Scale Sand Boa the other day. He got a 20 gallon long tank for it and a Exo Terra Heat Wave Desert Small UTH. The tempurature probe being right on the surface where the heat pad is registering temps of 100-102 degree F, and it feels very hot to the touch. He is using Aspen as his bedding, but I am worrying about the snake getting burned from the heat and having direct glass contact over the area the UTH is. Aspen seems to be too light and provides no insulation over that area as the snake is a burrowing snake. What would you recommend for us to do to prevent the snake from being burned? Any different bedding or anything else we can put over that side to help prevent the snake from having direct glass contact over that side where the UTH is?

I have kept them on playsand with no problems. I don't use the UTHs though because they do get so hot. I use an incandescent bulb from above. You can vary the wattage to achieve the desired temps easily.