" low blood pressure can contribute to cold extremities"
Indeed. Story of my life.
While low blood pressure is great for overall health and a factor that retards physiological aging. it's not so nice for those of us trying to keep our extremities warm!
To wit, two weekends ago with night temps that dropped just below freezing, I slept in my Western Mountaineering Summerlite (rated to 32), in a well-ventilated Tarptent Moment, wearing BPL merino base layers, R1 pants, R1 hoody with hood on over a merino wool cap, liner and wool blend socks, WM Flash jacket wrapped around my feet, and the bag hood cinched around my head, on a Torsolite + GG 1/8" thinlight, and I still had cold feet and slightly cool legs and outer edges of my arms, where they pressed up against the bag. Additionally, I was well-hydrated, well-fed (with hot food), and always change out of sweaty clothes and wrap up promptly upon returning to camp, or making camp.
My core was good, so there was no major problem, except that I didn't get the kind of sleep I would like to get.
I've since bought a pair of Feathered Friends down booties, which I used last weekend, and loved, but that wasn't a comparable test since I was sharing a double walled tent, and temps didn't drop below 40; I was warm.
As others in this and the other recent thread have testified, more and more I'm starting to realize that this is one aspect of UL backpacking where I'm going to have to ride the cusp between UL and just light, at least as far as winter bags go. I've got some winter Sierra trips coming up, and there is no way I'll be able to extend the Summerlite down far enough using all the UL techniques at our disposal.
Alas, such are the wages of low blood pressure.