Lots options as you can see. But if you are not planning on upgrading your existing system(s), then I'd do as others have suggested and set the lp furnace a little below the minimum temp that you want the rig to get. Then use the electric fireplace (if you have one) and space heaters. They will heat the place up pretty quickly.
On this subject, I might add the we spent the 3rd week of OCT in Asheville. The first 2 nights we were there the temps got down to 29 degrees! We did not use the LP furnace but just the electric fireplace and the 2 heat pumps. Living area thermostat was set on 69 and bedroom on 68. Bedroom unit rarely came on.
Point is we were shocked that the heat pumps worked in those tamps But no problem.
Our rig is designed for 4 season camping does have very good insulation - especially in the floor. Also, our main living area a/c-heat pump is tied in with the furnace. If there is a 5 degree temperature deferential OR the heat pump can't maintain the set temp, the LP furnace automatically kicks on.
I'm like you....I kind of get a kick out of cold weather camping, too. Enjoy!!!
