I'm getting a plexi lid made for my tank, so I can give you bit of advice... Find a car stereo shop that does custom work. They make a ton of stuff with plexi for speaker boxers. Found one in my area that will cut it to size, make air holes, cutouts for my lights, and even make a tapered edge on one side so the lid still locks in. Only charging me fifty bucks for it.

As for the other stuff, you've already heard... Absolutely no heat rocks. Ever. No exposed heat lamps. Your snake could get some very serious burns.