I had two thermostats; one to control the CHE and one for the UTH, on the warm/opposite side.

For the CHE, you want the probe abt the same level of the snake, but keep in mind, it you tape it to the side of the tank, it won't be AS accurate, b/c it'll read temp of the glass from the outside.

Mine was under the bedding of the hide, where Crystal usually stayed...but bedding is only abt 1-2" deep (or tape to inside top of hide?). That'll give an ambient reading of his environment when he's in the hide.