Interesting thread, since these are some of the questions we're asking, too.
We have two furnaces in our MH. The rear furnace provides heat to the bathroom, bedroom, and wet bay. I have a small electric heater in the wet bay for supplemental heat there. We keep the bedroom door closed during the day since the thermostat is there and use electric heat for the rest of the coach. These hints don't work well on an Airstream unless the thermostat is in a place where it can be kept cooler and an electric heater supplementing the heat in the salon.
One tip I heard is to make sure that there is an air return from the wet bay to the furnace.
David Lininger, kb0zke
Heartland mpg 181 (sold)
1993 Foretravel U300 (for sale)