Hi again, I like the rack, but, that much heat tape really worries me.
When using heat tape, you must consider the potential. Heat tape is not regulated by a set temp. It simply increases heat. So its wanting to add heat, to whatever the ambient is. Its constantly attempting to do that. (its drawback)
Of course a thermostat will regulate that. That is until it fails. Then that much heat tape will raise the temps FAST.
I would use much smaller tape. Amounts that do not have the possibility to overheat. You can still use a thermostat. But if it fails the tape does not have the potential to kill quickly or at all. In my baby rack, I only have a small corner heated by heat strips. A three inch by six inch corner on cages about the size of yours. And I use a reostate.
Worse case is, you will lose your house. Yes, that happened to a friend of mine. His thermostat failed, the tape fried the cage and snake room. He had a patio door leading into his snake room. He came home and noticed it was black, so he opened the door and had a backdraft or flashover or whatever you call it. It was not nice. The snake room ran out of air, when he opened the door, end of that story.
So use as little as possible, not as much as possible. In reality, snakes do not need much added heat. The key is room temperature.
Also, the design you used is better for controlled rooms temps and not so much for the use of heat tape. You have all but the front of the cage insulated with the rack, that will not allow for a choice of temps. If you use a regional heating source(heat tape, hot spots from lites etc. Its best to only inclose or insulate part of the cage. That is, have half or more of the sweater boxes expose to open air(room temps) to allow a range of temps. Cheers