The blind is 5x8 and very tight. I think I'll install a damper and see if that helps. The stove and the double walled pipe were very hot but I could easily hold my hand a half inch away from the stove. It just seemed that most the heat was going up and out the pipe. The pipe was hot all the way to the ceiling.
It was only 35 degrees out and I had to keep it on high to get any noticeable warmth. I didn't even open the vent, I think the heater would have been a net loss had I opened the 4 inch wall vent.
The windows fogged a tiny bit but not even close to what would happen with a buddy heater. If a damper can get the heat to stay in the blind, I think I'll love it.