oh before I forget... I did try something that didn't work out and I wanted to bring it to your attention so you dont try it.
I own a pair of down socks from Nunatak (converted teanaway booties). I got a pair of goosefeet down socks bootie shells with some OCF padded bottoms to convert them from sleeping socks to booties in the winter. Basically a failure. Warm when you are sitting in the hammock and when you venture briefly to go to the bathroom. But after 10-15 min your feet get cold in the snow. Better off going with official down booties like REI or others