I measure the hot spot in my tubs on the plastic itself, under the substrate. I figure they can get there if they need it. I usually go to 80 on the z's and pyros max, and as cool as I can get the cool side. (usually 70 in the summer and 60's right now.) If I had really long tubs I would probably push the hot spot up to the high 80's. If I do that now it raises the cool side too much. Now, my getula get a hot spot in the 90 range.

Joe