I also am in a drafty old place I found (you'll hate this part) but to solve the temp issues I needed to add 17" to the front as well as 4 inch at the back. The 17 doesn't get much over 86ºF so it will not ever over heat the snakes even if the t-stat fails. I needed to run the top and second down on one probe The middle ones on another and the lower on a third. The fourth controls all the front cool sides. Herpstat pro is what I am using 4' for the hot side and the 17 on the cool side.