I have the tstat probe in the middle of the rack right in top of the heat tape and the thermometer probe i have it inside the tub where my hotspot is and i have both taped with black electrical tape
also i have a another thermometer next to the tstat probe in the same place in the heat tape and its like 1.5 degree up then the tstat temp
im using the temp gun in top of the substrate cus the acurite probe is also in the top of the substrate