I don't hear much about this guy on here and I don't know if you or the majority on here like what he say's or don't agree with him. I find him interesting and sincere and he does have a lot of experience and say's he's learned a lot through mistakes and that is Brian Grundy. He has You Tube video's (one in particular) about husbandry. He say's belly heat in racks is good and back heat is bad. Anyway that is what he say's. I don't agree with everything he say's necessarily.
But if I had a rack (and I'm glad I don't) and was talking about heat tape. I think I would stick to putting it on the bottom for belly heat. Or find another method besides heat tape for heating from above (non-belly) I don't think a heat tape on the back wall would do them much good for heat or anything. I don't know much about rhp's to say anything about that idea. If you worry about burns you might want to go with ultra-therm heat pads instead. If the thermostat fails even they say it won't burn the snake. Till you hopefully soon catch it, unhook it, and get a new thermostat.
Glad you asked the question. I will find it interesting what those with racks and experience will say.