I know a lot of people swear by 80 degrees cool side, but the Barkers in their book say down to upper 70's is fine. I shoot for 80, anyone have any first-hand experience?

You could try a 25 watt "party light" (blue/purple/red bulb available for $1.00 at pretty much anywhere) just kind of pointing down at his tub to warm the air around it. Obviously don't melt it and don't cook him, but this could work. You may have to mess around with the right distance, get one of those clamp on domes. Warming one side of the tub could kick up the cool side that extra 2 degrees.

JonV