Too much for a foamie?

Great forum!
I'm dreaming up a homebuilt and really intrigued by the foamie build. But. ... Can it handle a 12' long x 6' wide and 6 1/2'structure? Do i need to have some supports across the roof or sides? Not exactly a tt, but that's what it will take to meet my need. Will likely do an canvas/tb2 exterior.
Also, can it handle the heat of a typical camper gas refrigerator and furnace? Any special considerations? I would have them stacked in the same area and would vent to the outside like regular campers?
Thanks!
I'm dreaming up a homebuilt and really intrigued by the foamie build. But. ... Can it handle a 12' long x 6' wide and 6 1/2'structure? Do i need to have some supports across the roof or sides? Not exactly a tt, but that's what it will take to meet my need. Will likely do an canvas/tb2 exterior.
Also, can it handle the heat of a typical camper gas refrigerator and furnace? Any special considerations? I would have them stacked in the same area and would vent to the outside like regular campers?
Thanks!