Flexwatt is technically a UTH since uth stands for under tank heater, which is what flexwatt is.

I put flexwatt on shelves and sit tubs on top of the flexwatt(to the dismay of at least one person, lol) controlled by a thermostat, works well and I actually like the locking lided tubs better than my rack

Taping the uth to the tub makes it difficult to thoroughly clean and sterilize the tub when needed.