Flexwatt heating issue

[Quacking-Terror]

I switch it to the other piece, and the temp of that piece drops, slowly of course. The temps are pretty constant across the entire tape. I mean, I know its going through the tub + half inch or so of substrate but it still bothers me.

I just checked the temp on top of the substrate and against the bottom of the tub. It's between 77-80 on top of the substrate and 82-87 on the bottom of the tub.