Almot,
No matter what the outside temperature, I open the rear bath ceiling vent all the way and control the inside temperature by opening/closing windows at the front of the trailer.
In our 22' trailer, the Wave 6 on low produces too much heat to run constantly when the outside temperature is above about 60 degrees. In those conditions, I usually just run the furnace for a couple minutes to take the chill off. If I know it is only going to be that warm for a couple hours, I let the bath fan thermostat regulate the heat by turning on the fan and dumping heat when it gets too hot. Wasteful of propane and electricity, and it doesn't regulate over a very narrow temperature range, but it's "almost" automatic.
I find it easier to use a BBQ (or similar) long stem lighter than the built-in peizeo lighter to light the Wave heater.
Hope this helps.