when i set my rack up i placed my temp probe for my thermostat directly on the flexwatt in the second tub slot from the top its a 4 tub enclosed rack and i have belly heat also. i had some crazy high temps at first but after a few hours they seemed to stabalize around what the thermostat was set at. im thinking it just took awhile for the end of the temp probe to get warmed up and once it did its been good ever since. i have been checking mine three to four times a day and so far after the initial set up it has been ok. i know its not much of an answer but hope it helps