I already had stuck the UTH to the glass before I knew I needed a thermostat ( got this all set up well in advance of actually getting my snake). Yes my temps at the glass BEFORE the thermostat were 158F!!! I didn't want to ruin the pad so I have the probe directly on the glass inside the tank under the substrate. I also know with an on/off type thermostat I will have a bit of temp fluctuation, mine seems to run about 3-4 degrees. Just don't understand why I have to keep fine tuning it to keep it from creeping up.
I heat the ambient temp with a lamp and red bulb on a rheostat on the screen cover so my UTH is only for the hot spot under his warm side hide.