Get a one foot section of 11" flexwatt for the warm side. Plug that directly into the thermostat. Set it at about 93-94.

THEN, go to Home Depot and get a Lutron Credenza dimmer(plug and play, no wiring) for $11.

Plug a 2ft section of 11" flexwatt into the dimmer, and then plug the dimmer into the thermostat. Dim it down until you reach the low 80s.

All you have to do is leave it alone once you find the right temps The thermostat will take care of it for you. Be sure to tape the dimmer in place so it doesn't get bumped.

I have used this method on alot of tubs if they were in QT and the room wasn't heated. Works awesome.