I've used UTHs like that before on sterilite containers. O_O It was just for a night, but it worked really, really well. I would probably double stuff your substrate so that there's a cushion between the snake and the uth. That way you don't risk any sort of overexposure. Just be cautious, y'know? As a quick fix for a few days, I'd do it.

MAKE SURE YOU WATCH TEMPERATURES and snake responses.