Last night I put my Montbell super stretch ul3 inside my western mountaineering megalite to see how it would do in the cold, temps were to get down below 0°F. I xc skied to the woods about a mile behind me and set up my old zoid 1 in a clearing with some wind protection with which I did get, I would say the winds were never stronger than 5-8 mph where I was. The temp dropped steady from 18°F at 9pm to -5°F by 6:30-7 am. I slept in a light base layer and socks no hat with a 1" thermarest pad under a ridge rest. I started out with the montbell fully zipped and the WM 1/2 zipped top open and as the temp dropped I cinched the hoods closed and zipped up the outer bag. I was warm all night except my nose. I could maybe push this to -10 before adding additional clothing. With my ski bibs and puffy and hat I'm sure I could push this to at least -20°F. These two bags fit together like they were made to be together the megalite is roomy and the ss pulls itself around you. Earlier in the night when my legs were getting warm between I had plenty of space to stretch the ss bag to get cooled down this was a very roomy comfortable combo. I do sleep a little warmer than most and I'm 5'10" and 225#. I know others were asking about combining bags recently so I thought I'd report my experience the two together weigh in at 3lbs
