This is the way I would set it up: tape probe to bottom of tank in the middle of the biggest part of your UTH. Then tape on your UTH. I even tape on the sticky ones so I can remove it without ruining it. I use packing tape around the edges only. Then I put a thin layer of bubble wrap followed by cardboard, both to the size of the entire bottom. The bubble wrap and cardboard keep in the heat and reduce thermal cycles.
OP, Taping the uth on instead of sticking it is a good tip. To add to that you can place foil on the sticky part of the uth.
KMG
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