I was the one who slept in the shelter. Temperatures were single digits and I did use about 5 or 6 pieces of oak the size of my thigh for the night. I did get a good coal bed going before going to bed so that helped, I wouldn't start the fire as you decided to get into bed. Regarding the warmth of the shelter it was actually too hot. Compared to the debris shelter I stayed in when it was in the 30's this one was way warmer because of the fire. The back was to the wind and with the exception of one small hole that could have easily been covered there was very little wind on my rear. I had the sleeping bag opened completely and was half out of it until the last couple of hours when I said screw it and let the fire go. I only did this because we were leaving and I didn't want to carry over water to put out a perfectly good fire before leaving.
The reflector was as close as it could have been, the bottom log was starting to get charred and any closer would have caused things to get even hotter. Two things kept waking me up that night, the heat of the fire and the fear that I was going to spontaneously combust. Thank goodness I had a row of logs keeping me from rolling into the fire because I sleep all over the place.
If you haven't stayed in a shelter you simply have to. A big thank you to IA Woodsman for taking the time to help us with our shelters. He is a heckuva guy and a seasoned woodsman.