I've reached the end of my efforts to tweak my BP setup. You can tell me what you think, but I don't think it's getting any closer to perfect than it is now.
I have a 5 mo female ball in a 30 gal tank. I have a screen lid with peg board attached to the underside, and a little more than half of the holes covered. I have a Herpstat II controlling two pieces of Flex-watt secured to the underside of the tank. The probes are fixed securely to the inside bottom of the tank, near each back corner. No problems with her messing with them so far. 1/3 of the FW is set to 95 deg, and the other 2/3 is set to 85 deg. Those are the temps at the glass, and the Herpstat usually ends up a few tenths of a degree below them. She is not a burrower, yet. She has a ceramic pot hide on the hot side, and her water is on the cool side. My substrate is aspen thats spread pretty thin.
My variations, which I can't seem to improve are as follows. I've found the Flexwatt to run a few degrees cooler at the edges than it does in the middle. If I get 94 at the edge, I can get up to 97-98 in the middle. These are infrared temps with a heat gun, at the glass. On top of the substrate the temps are usually around 90.
I live in central Florida, where we have high humidity. My humidity levels fluctuate between high 40's to low 70's.
Again, I think I'm at the end of my efforts. My girl seems to be happy in her home. She has an excellent appetite, and seems to be thriving. Considering what I've spent on the whole setup, especially the Herpstat, I think I'm done.
Thoughts, comments, suggestions?