One thing I found out about the flexwatt is that since they weave it over and under every shelf, the closer you get to the end of the flexwatt the cooler the temps get. Because of this my racks are actually cooler at the top shelves than they are at the bottom shelves. I was confused by this at first knowing that heat rises. Are your temps the same in every tub? I believe the longer the length of flexwatt, the more wattage it loses as as you get closer to the end. Must be the same principle as losing wattage if you have a power strip plugged into a power strip etc etc..

I use Helix thermostats and accurite thermometers with a bunch of smaller accurites for every other individual tub. A 6:1 tempgun for measuring accuracy. I still have issues with maintaining temps sometimes. My ambient in the biggest tubs is always about 79 while in the smaller tubs its over 80. I keep the snake room at a constant 80 degrees to help with this. The only way I can think to improve the temp is by starting out with no holes at all punched in the tubs.