I'm trying to cut weight and volume for winter hiking and I've come up with this:PHD minim ultra bag- theoretically good down to 46, GG nightlight torso or neo-air on a cold weather ccf full length mummy cut bag inside a Ti goat bivy under a Gatewood cape. Inside I'd be wearing merino baselayer, micro fleece mid, PHD minim ultra vest, patagonia down sweater, my hiking trousers, down inner trousers, thin socks and Goosefeet. The plan is to camp on snow at temps down to about 23 probably in fairly exposed/draughty spots. Because this is Britain it will be damp cold rather than dry cold. Any input?