I use aluminum tape on the edges as well. However, for my racks, I built metal flashing that encases the tape so that the tubs slide smoothly over the metal flashing and does not place any wear on the flexwatt at all. I place my probe on a piece of plastic the same thickness of the tub and then tape it to the tape or flashing material. This helps simulate the acutal tub temps a little more closely. I always check my temps with a heat gun periodically to make sure it is working correctly. Hope this helps.