I have never had any luck with the ZooMed rheostats if that's what you have. Temps have always spiked like crazy. If you're having problems you can get a probed thermostat when you have the $$. Without spending a ton you could pick up a Reptitemp R500 for around $30 or a little more.
I would add binder clips for the sides of those tubs. The longer one at the bottom will have more flex and makes escapes easier without clips. Losing a snake because you didn't use a 10 cent clip stinks. Glad you're liking the tubs.
I know about the clips but I have this really heavy statue of a dog on top of it which keeps the lid down so I don't think he could escape but I'm pretty aware and cautious of that happening.
Where could I get the Reptitemp? The Zoo Med dimmers are horrible lol.