When making my racks, I tape in a wooden shim (Lowes or HomeDepot sell them for leveling doors and windows)This serves as a backstop for my tubs. They wont come in contact with the connector clips or push on the temp probes either. I also lay 3 layers of aluminum tape in the front and sides of my flex-a-watt so I have a "wear" surface.
The tubs are still plastic and can burn and melt
I have been thinking for the past couple days on a sprinkler system for a snake/reptile room.
My worry with a sprinkler system is the potential to drown some of the collection. But if you have a "mini" roof over the racks then you could now be protecting the fire
Maybe design a rack with a built in system with nozzles directed away from the tubs. Then what would the costs be for such a system and how many people would install them due to cost??