The other issue is the chance of pulling the probe off when moving the tub around if the flex-watt and probe for t-stat are attached to it are very good flex-watt maxed out very hot in some cases I have 4 inch that hits over 190º unregulated. If you have two snakes why not use a uth directly on the tub? you then have more options to control ambient and cool end temps too. Ultratherm are very safe as they are designed not to heat over 100º so even if the probe did get pulled it is still will not cause massive burns and fires.