Hi, I have an Accurite and UTH too. An unregulated UTH will heat up over 100 and could possibly kill the snake. It MUST be plugged into a thermostat to control the temps, or at least a light dimmer to tone it down. I use the ReptiTemp 500R with my UTH, and it works well.

Re. the probe of the Accurite, I've seen different suggestions here: Directly on the glass so you'll know how the temp there; or on top of the substrate so you know the temp of where the snake actually is.

I've gone for the middle: Between the sheets of newspaper, which is topped with a single layer of paper towel. Really, my substrate is no more than 5 or 6 sheets of paper. I see you have about an inch of substrate (your tank set-up is beautiful, by the way), so it'll be cooler on the top of it than on the glass.

Before I switched to newspaper, the inch of substrate I was using created too much of a temp difference and I was going nuts constantly adjusting the 500R. Ever since switching to such a thin substrate, the temps have been more accurate and easier to adjust/maintain.