Thank you both for the advice! I'm gonna go with putting the CHE over a mesh, glad to hear it doesn't mess up the humidity too much. I was also thinking putting something so hot next wood is a tad sketchy, plus having a wooden guard around the CHE would probably just make it even harder to heat the tub.
Thanks for the notes on the thermostat probe placement and zip ties as well, super helpful! This community is the best resource a ball python owner could ask for.
EDIT: Also another quick question -- would you recommend putting the CHE on the cool or warm side of the tub (or the middle)? I have the most trouble getting the cool side's temps up to at least 75F since that side is next to an outer wall of my house and a window which makes the air cooler.