I have a force10 Cozy Cabin Heater
Installed in my aluminum boat. My boat is smaller than my camper, but is totally in-insulated, and even in the low 30's it will warm the cabin up to warm enough that I have to take my jacket off. Even with the stack, the propane version emits a fair amount of moisture, so if I were to consider a heater made for a boat to use in a camper, I would consider either the diesel, or better yet the solid fuel, as it is better for use boondocking to save propane for the stove.
Garry in AK