Question about back heat

I recently purchased a hatchling rack from RBI and it came with back heat. I'm regulating the flexwatt with a Herpstat 4 and I have the temp set at 88. Now the bottom of the tubs measure between 87 and 89 with my temp gun but the backs of the tubs are measuring ~100 degrees which worries me. Any advice?

Where is your T-Stat probe located? I know with back heat the tape will usually run at quite a bit higher temp than the hot spot in the tub. You lose a lot of heat in the transfer.

EDIT: Just re-read your post. So the back wall of the tubs are reading around 100 degrees? What do you have the Herpstat setpoint at?

Correct Slim. The back of the tubs are measuring at ~100 degrees, but the floor of the tubs are measuring right on at between 87 and 89 degrees even right at the point where the bottom meets the back, but once I move the temp gun up the back it goes up to 100. I have my herpstat set at 88 degrees.

Oh and I have the probe for the t-stat located about 1/2 inch from the flexwatt as per RBI's instructions.