buy the uth. and a thermostat. with the thermostat dialed down to 90-92 degrees there will be no issues with it melting. the reason why there is a warning on the uth is because when it is not regulated by a thermostat it can reach 120 degrees. i also do not suggest sticking the uth to the tub. instead wrapping it in foil and placeing it underneath. i stuck mine to it and now realized i cant remove it for cleaning etc...
goodluck. feel free to ask as many questions as you need!
WELCOME!