Ive never heard of fires in snake rooms because the heat tape got to hot. I have heard of fires from faulty wiring but not from the heat tape itself. Some of my racks have back heat, some have belly heat and some have heat cables and i have never had any issues
Go cover your back heat 100% with foil tape and see how much that surface temp is lower than the actual tape temp underneath. I did this on test and the flexwatt hit 150F