We just built a new rack and are using 4" flex-watt. The rack held temps great the first night. Our hot spot as indicated by the temp gun is 82. We are running everything to a Helix. The Helix is set at 98 and the Helix probe is resting on the flex watt tape.

The bottom of the tubs when slid out are warm to the touch. However, inside the tub (where the snake is laying) is significantly cooler.

Do I need to upgrade to 11" flexwatt? I don't know how to get the hot spot or ambient temps up. The flex watt does not seem to be penetrating through the tubs.