Back Heat Thermostat Issues

I am just wondering how you guys have your BACK heat thermostat setup?

I just got a new 28qt Rack and decided to try out back heat. I have a strip of 11" flexwatt going down the back.

I have the Herpstat probe taped to the flexwatt on the third shelf down. The Herpstat is set to 110 degrees (my belly heat racks are only set to 94-98!) and the flexwatt temp guns at 105 degrees. HOWEVER the very back of the tub is only 87 degrees!

Do I just keep upping my thermostat until I get my desired 95 at the back of he tub? At this rate, I'll have to set it to 125 or 130 degrees!

Or do you think I should just put the probe at the back of the tub and set it to my desired 95? But if I do this, I fear the flexwatt will get too hot?

What is the "danger zone" temperature for 11" flexwatt, is there even one? Is 125-130 degrees too hot you think? Can 11" even get this hot?

My room temperature is about 76-77 right now.

Thanks, first time dealing with 11" flexwatt and back heat.