The problem is that you have a tall tank, is there any way you could put the CHE inside the cage and have it lower so that it heats down near the substrate?

You would need a screen cage around the CHE and have something over it to keep the snake from getting burned. Either insulate the top so the snake can climb on top of the CHE cage or have something that keeps the snake off of it completely. I have an idea that would probably work to get the CHE cage lower but it would be a little work.