I'd like to stress the rheostat/thermostat as well! I was using a UTH alone and thought my temps were fine, but when I got decent thermometers (Accurite brand from Wal-Mart) and put the probes under his hides the temps on the hot side were up to 101 degrees!!!
I was just using a Flukers thermometer/hygrometer combo in the middle of the cage, and it was reading in the mid-80s during that time!
1.0 Husband (Aaron)
1.0 Normal (Milton)
1.0 Puppy (Ollie)