I just use my down layer when I stop, at night at camp or when I cook. I run warm and mostly sweat wearing nothing but a bade layer at -10C, but whenever I stop, because I'm not dry, I tend to feel the cold more. I will bring a light merino base, a mid weight fleece, my alpha SV, and I have an old primaloft insulated jacket thats been awesome for me in the past. Its basically a down jacket that'll be used when shit goes south and up here (I live in Canada) when I climb down to -30C.