I just attempted winter hammock camping for the first time up in the Whites this past Monday. I got a 0 degree underquilt which combined with my 20 degree Kelty was more than enough for the 20 degree temps I encountered. In fact I was quite warm so that bodes well for future colder trips. Too bad my tarp and knot skills are rather dreadful - that's the next thing I need to work on. There was snow late in the night and my tarp wasn't set up correctly to deal with it. However overall I was pleased with my efforts and wish you all luck with your winter camping adventures.
Interesting!! Good for you.
Did you use a foam pad with the underquilt?
What was the wind situation during the night? Seems like wind chill might be an issue when floating in a hammock in winter.