x2 on the vent pillows. I'm also going to try the bubble wrap for the windows this deer season. I've only camped with night time lows in the mid 20's, but the heater did just fine. Of course, once it gets to that level consistently, I go ahead and drain the water lines just in case. Not sure if you have utilities or not there, but if you use a supplemental electric heater, that could affect how much you camper system runs.
'01 Ford F250 CrewCab