you should find out the surface temperature directly above the UTH if you havent already. to do this simply tape down a thermometer probe directly to the glass on the bottom of the inside of your tank. now using tape inside the enclosure is usually not recommended but if you use aluminum foil tape and stick it down properly it will never come off. if you dont have this tape or dont want to use tape then figure out a way to keep the probe fixed to the glass so that you can find out the exact surface temperature that your snake may come into contact with.