A few things come to mind on placement of the probe.


when the temp probe is close to or mounted on the flexwatt the temp will recover slower because when the heater turns on it will heat up the probe area to quickly and not give the true air temp or tub temp. If the probe is at the tub area the flexwatt will have to stay on longer for the heat to reach the probe and therefor give a true temp at that location.

It's like putting your thermostat in your house right on the heater. The heater will come on and run for a min then turn off but you will still have a cold house for a very long time.