Running furnace with slideouts in.

My trailer has three vents. The one in the LR/Kitchen gets covered by the slide but the one in the bath and BR remain unobsructed. As far as air flow goes, with the slide in, this will just send more air through the frontmost vents. It's hot air, not a hot element; it shouldn't be a fire risk so I can't see what problems it would cause by running the furnace. My unit has a "Cold Mountain" package where the tanks, etc are supposed to be kept from freezing when the furnace is running. I was told you could even tow it with the furnace running to keep it from freezing (I know the propane on/off is a debatable issue but this isn't about that).

I'd like to hear from others about this. Anyone heard from the manufacturer on it?