I'm almost done putting together my homemade rack and pretty much just need to set up heat. It's going to hold 18 tubs and my plan was to run 6" heat tape across each shelf which comes out to around 34', but will be a little shorter to leave room on each side. My question is at what point will you start to lose efficiency? It seems like running that much heat tape there is the possibility of each shelf having a different temperature. Any help is appreciated as I haven't been able to find the answer myself lol.