Best way to heat tubs?

Thinking more and more lately about switching Bo, my bp, to a tub, I've finally got to the point where the humidity in his tank is OKAY but to keep it steady I have to mist it multiple times a day and I'm not sure how long I can keep that up.
So I'm wondering what the best way to heat a tub would be. I've done a bit of research and I'm thinking my best option would be two UTHs, one on each side set to different temps, but I'm looking for more info. Can you use a CHE with a plastic tub? Would that just defeat the purpose of a tub to up the humidity by drying it all out?

UTHs on both sides would work great for belly heat but the biggest problem I've had with a plastic tub is the ambient temp. So far I'm handling that problem by heating the whole room to 78F with an oil heater.

Several people have told me they have successfully installed CHEs to plastic tubs. Here is a very thorough tutorial:
http://rainbowsnakes.tumblr.com/post...ial-part-three

People who have used CHEs with tubs also say that it doesn't affect the humidity much, as long as you don't cut an overly large hole in the lid for the wire mesh that the CHE rests on.

Also try to get one of those tubs that are around 6 inches deep and not the tall ones, because all the extra air space is hard to heat.

I think I'll go with the CHE then as I'm not able to heat the whole room, that's a really helpful tutorial, thank you!