try to get shelter to about a kilo or less.

really think about clothing choices. I've taken to carrying the whispiest of nylon pants as long pants. I did a tour where I eliminated any warm layers for the lower half except thin leg warmers and jogging shorts under a nylon shell. Marmot Driclime windshirt are wildly effective as a mid/wind layer, and packs up very small for its warmth. Driclime, a shell and a down vest is very efficient space/weight wise.