DIY wood stove from a surplus ammo can.

Here's another option to heating the tiny camper. This kind of wood burning heater would be very very light when compared to the weight of an empty 5-gallon propane tank. Just another idea tossed into the hat.

Weight is so critical concerning the camper. I don't want to drag a heavy camper across a muddy field and wound up getting stuck. Been there and done that. Used up a roll of roll roofing to get out. A wrecker to pull me out would have been real expensive that far out in the sticks. A roll of asphalt roofing was about $20 back then.