My love affair with bivies started and ended in one Septembers bow season in NW Montana. I spent 5 days in the Swan Range chasing Elk. It went from 70 and sunny, to 50 and rainy, then 35 and snowing. That trip was in the top 5 for "sucked the most" That was the end of me thinking Cameron Hanes knew what the [bleep] he was talking about. Now I'm of the opinion that bivies are for emergencies. Something to consider... A Kifaru Supertarp without an Annex weighs about what most bivies does. It also sucks way less than a bivy.
sleeping with clothes on? I always have underwear on, socks, and a shirt when I'm in a sleeping bag. Once it actually starts to get cold out, I usually have on a 200 weight merino wool pair of long underwear on, and a henley merino top of similar weight. My new favorite socks are the Smartwool PhD's of midweight design. If I think it'll be cold enough that I'll be wearing more clothes than that to bed, I take a warmer bag.
However.... Springtime in Montana can get dicey, and I recall one trip during Spring Bear that I wore all my clothes inside a WM Badger (merino base layer, 320 weight merino fleece, and a downie jacket) I don't remember being cold after putting on all the clothes. But then, there's enough room in that bag that I wasn't tight anywhere in it...
That was before I became a full blown "non-classic-backpacker" and had heated shelters. Now, wet clothes, wet bags, shivering, being cold in a tent, or having life suck in November are distant memories.
My favorite tent right now is my Seek Outside BCS1. Tent, stakes, and center pole (carbon fiber)in an EdT 10-5 sack is 3 Lbs 10.4 ounces. My C stove from Ed goes 1 pound 13 ounces. 4 1/2 Lbs for a heated shelter that I'm sure is more square feet than a floored tent of the same weight. That leaves enough room in my pack to carry a 19 ounce axe to play with
