Back heat is good because the only part of the tub that actually touches is the rim around the top of the tub. It is definitely easier to trust belly heat for obvious reasons, but I am having great success with back heat so far. As far as the tape over the metal edges, this is where the shock will be coming from. If you cover the exposed areas it will close the circuit. What do you have on the edge of the heat tape that is opposite of the end with the clips? And yes I would check the heat tape from time to time for wear. I would actually tape it straight to the shelf also. Electrical tape is pretty easy to work with. 14 hour shiftsgood luck with that