Wow. That is a pretty impressive camper, and quite well built to use in extreme cold conditions. This reminds me of the old Bigfoot campers, built for use in the Canadian north.
As suggested earlier, propping up the "tub" for winter would be good.
The only thing I would add to my earlier post, is the following:
-since camper will be used/stored off truck, pre cut 2 inch thick pieces of XPS polystyrene closed-cell foam insulation to encapsulate the camper's tub and under-wing areas. Store the pre-cut foam in the camper and assemble it at site, using 2-inch wide house envelope tape (I used this stuff when I stored our camper outside over winter for the 1st and only time; the tape held up under persistent -36C and 90 KPH winds), XPS friendly adhesive, and a belt (a ratchet tie-down around perimeter of insulation-clad tub, for safety). This would add a fantastic barrier against ground radiated cold, and frost advection (the coldest air is closest to the ground, so the camper tub, being off truck, should have extreme insulation there). In spring, just remove and store foam for future use. Measuring and cutting the XPS should take only an hour or so; assembly should be really fast, too, with 2 people working at it.
As Joerg mentions, keeping the propane from freezing will be the biggest hurdle. The large propane cylinders would need their own insulated containment.
