OK, this might sound stupid, but with it being insulation foam, is there any danger of the heat from the lamp(s) melting it and causing a fire? Since it's on the OUTSIDE of the tank and not inside, I'm assuming there's no problem with regard to the snake (or turtle - if I use it for Sasha too) eating it?

A lot of people have suggested plastic on top, but I couldn't figure out what kind of plastic to use. This makes a bit more sense to my addled brain. Thank you (and thank you in advance for answers about heat, melting and fire).

I have used the wet towel method with pretty good success, i put about a cup to half a cup of water on it each morning and my humidity stays right at 50-60%. towel covers about 2/3 of the tank with a ceramic heater on the other side, change the towel every few days, so no mole issues. i've also thought about using disposable diapers (don't laugh) they hold moisture well and release it slowly over time if exposed to air. also doggie piddle pads (for house breaking ) come in flat sheets that work the same way, both would be soaked (in water of course) and put atop the tank. garden supply shops (even home depot and lowes) sell a nontoxic reusable polymer that you mix with soil it holds like 200 times its weight in water and again will release it slowly, this could be mixed into the substrate or placed into a shallow container with a screen over it (to keep snakey from playing in it). could be attached to the side of the tank by plastic or wire hooks, suction cups, or even hot glue. it is cheap enough that if it went into the substrate you could just throw it away and add a cup full at every full bedding change. of course i'm an engineer so I like to make easy things complicated. wet towel still works best for me.