I've been sleeping in an Eno doublenest and more recently, a wbbb with an old thermarest backpacker from the 90's. it's kept me from freezing but that's about all I can say. My butt and shoulders and at least one foot get really cold and it's not really comfortable. I finally broke down today and ordered the 20F full-length Zeppelin. I got black fabric on the inside, purple on the outside. I opted for the treated down, draft collars and two ounces overfill. Can't wait till it gets here!