Taping down Flexwatt, and placement of probe in rack.

[hoax]

Tape the edges.

As for the probe place it on the middle shelf, taped directly to the heat source using foil tape (under a tub might be a problem when opening and closing the said tub)

Exactly what I was going to say.

I got my rack from RBI and the way Rich runs it is you can tape the probe off to the side where it will be out of the way. Also the flex watt is in a laminate so you don't need to worry about protecting it just be sure it stays down or it could tear things up.

Mike