We have our snakes in tanks (more visually appealing and my BP seems to like watching us and TV). I stick a ceramic tile over the ZooMed UTH (no FlexWatt yet). That reduces the temp by about 10 to 15 degrees by spreading it out. Then adding a layer of substrate (CareFresh Bedding) reduces the temp to about 90 degrees. I have a ZooMed thermostat running wide open (probe taped to ceramic tile under warm hide). It only kicks out if the temp in the room gets too warm (over 80 degrees). If he does dig into the substrate it's only about 100 degrees, not high enough to burn (I hope).

It's not perfect but having layers over the UTH reduces the possibility of thermal burns.

I learned this from a guy who's kept and rescued all kinds of herps for over 30 years. He never uses thermostats and adds layers of substrate (indoor/outdoor carpet, etc.) to regulate floor temps.