The thermostat is working just fine, that's the problem. It's keeping the ambient temp perfectly, it's just the surface temp being directly under the CHE is being affected.
I should clarify, I have the hot side hide under his CHE so the top of the hide (where I'm measuring with the temp gun) is closer to the CHE than the ground.
I am only using a CHE on a thermostat. I have a 40 gallon tank, tin foil on the top and insulated sides to keep in heat.
It sucks cause I originally had just an UTH but that did diddly squat for the ambient temp especially with the cold weather so I replaced it with the CHE and now that the ambient's good the surface temp's too high :/