We are after two different things, as I hunt the backcountry in montana...so weight is the key, but when I hunt during gun season (prefer archery season, 17 days and 16 hours for me to go

)
When hunting gun season, we use a 12x12ft. wall with Stove, but we like Cherokee said, use a propane, great big buddy heater...and it can run all night long, has an oxygen sensor in it, and we run an oxygen sensor on the ground as well (propane, and most killer gases are heavier than air)
So, would suggest propane great big buddy, wiht a 40lb tank and should last you around a week, running it at night...
The great big buddy, as a fan in it, so it circulates air...
and if you go with canvas, I would suggest the tarp over it trick for insulation as well as protection...
MTdream