I recently posted a test for of BMBH/MWUQ at 12-16*F, and thought I should post a summary here as part of the official test and for long term ref. Nothing much new here for you have already read the other post.
Quick summary: warm and comfy on my back, legs and feet with the JRB BMBH and Mount Wash. UQ, and extra comfy all night on side and back with the combo of JRB Mt.Washington UQ and Bear Mt. Bridge Hammock. Low temp about 12*F
I had one of the best, most comfortable cold weather nights ever in a hammock last night, and definitely the best one ever in my back yard(where sleep is always a challenge for me, unlike on the trail).......................
About 1030PM I put a hot water bottle in my hammock. I noticed that the underside of the tarp and outside of the UQ had a heavy layer of frost on them already. About 11pm I sacked it at about 22*F with a forecast for 15*. I accidentally got my jacket a little damp on the back by contacting the frost on the under side of the tarp, and caused it to "snow" a little into the hammoc as I knocked some frost loose. I had on a few layers top and bottom a balaclava and hood on my jacket. I pulled my Golite 20*( maybe just a touch optimistic rating, but close) quilt over me. I had PG booties and space blankets and pads handy, but used none of them. Apparently I was out pretty quick for me. But I realized after 15 to 30 minutes, and just before passing out, that I was very warm, and very aware of a nice warm sensation on my back. Though as I warmed things up with body heat, I would occasionally be aware of cold butt syndrome. But that went away pretty quick.
I woke up about 330AM. I think probably because I was just barely cool, definitely no longer toasty warm. Though I think it was mostly top side coolness, but I'm not certain. I decided to get on my side and pull the quilt up over most of my head ( it's not long enough to completely cover my 6'1" frame, sadly, but will cover all but the very top). At this time I noticed that the top baffle( top several inches) of the quilt, the Pertex Endurance section, was quite wet from condensation from my breath. No matter, I quickly warmed up quite nicely and went back to sleep, feeling very comfortable in all positions during this night.
I woke up again about 430AM. Once again aware of being just slightly cold. It felt like it might be top as well as bottom slight cold. I debated putting in a pad or my space blanket. Instead, I decided to get up and pee and get a warmer bag. Pretty soon I was back in with an old PG mummy NF bag rated at 5*F, but this time no hot water bottle. I got on my side, pulled the wonderful hood over my entire head and made a small breathing hole, and was instantly nice and warm. Then I decided to get on my back, which meant getting in the bag. ( the hood really interferes with quilt use with back sleeping, and I get a poor shoulder/neck seal). So I got in, zipped up and cinched the hood and neck collar. Luxurious warmth, top and back, off to sleep. Got up about 7AM, went in and made coffee. The official low was 16*F at a nearby weather station. My thermometer showed about 11 or 12*, and has proven fairly accurate.....................................
This is a really good set up, and I think I could have gone a bit lower and been OK. I was impressed that I never had cold feet, even in the light quilt, and with just one layer of wool socks. And no matter how I rolled around, to either side or partly on my side/partly on my back or totally on my back-- there were no cold spots- just some cool ones for a few minutes. This includes my arm or elbow or hand which might have been under my pillow or above my head, and might not have been insulated with many systems without adding a small pad.
This would be great for even much colder temps by adding a VB or SB, or with a pad added to the superior functioning pad sleeve of the BMBH. That combo would be a candidate for one of Shug's -27F adventures, I suspect. Or I suppose, if you couldn't stand a pad, another quilt ( or PeaPod) could be suspended below this one for below zero temps.