Ok - here's the problem with the sock as is. If I leave the sock unfurled, I have no condensation. If I have the sides pulled up to hug the hammock (with a small 2-3 inch space), I had a small amount of condensation on either side of my head. Not a lot, just a small film from my breathing.
I looked closely at the underquilt for signs of moisture, but there was none. The bottom of the sock was dry. I guess there's a big enough temp difference with the sides pulled up to cause condensation. I'll make a "breath bib" or whatever it's called and try again tonight. The temp last night was 26*.