My suggestion is to avoid a heater with too much mass unless that mass is very low heat. When I first got dual temp control I tried a small ceramic hot plate. When the thermal probe read the cut off temp it would shut off power to the hot plate, but the temp in the freezer would continue to climb. The freezer would cycle on and run until it was to cutoff, then bang the hot plate is back on, and round and round we go. Temp swinging like 30+º. I switched to the heat pad and no problems. After countless random checks my temp is always within 2º of what I have dialed in, which is X with a 2º lag but no deadband.