So, for the folks who are following this and figuring it out, the point is that with IX on the outside in such extreme cold, you run the risk of trapping moisture in your insulation, where it will condense and freeze. A vapor barrier right under the hammock, like a CCF pad, or a Baby Orca, or a space blanket, will prevent that.
Someday Iíll have my own Molly Mac single layer IX hammock sock and was interested in your use of a diamond fly. Typically a much larger tarp is used for the winter season. Do you feel the combination of the diamond fly with the sock was adequate? Was the tarp even needed? Any breeze at all?
http://www.stc-hike.org/ Susquehannock Trail Club web site - PA STS trail info
I think I could have gotten away without the tarp, but would have wanted it pitched if it had snowed or was more breezy.