Never been in a hammock so I don't know the issues there but consider how much warmer and more comfortable mittens are than gloves of any real thickness.

I find it's always best to minimize moisture in my sleep. (And I'll sleep in damp/wet clothes so they are dry the next morning.) In my tent, I'll use the bag as a blanket until I get cold when rolling over. Then I zip up as far as needed. At some point I stop turing inside the bag and start allowing it to turn with me (wearing the bag). When it's really cold, my two big concerns are the orientation of nose to opening and draft tube to zipper. Even then, rolling over is useful for evening out any uncomfortable temperature variations.

Then again, I guess you wouldn't get that blast of cold air rolling over in a Gumby suit. But, that blast is also a useful way of letting excess moisture escape. We all want to be warm but at the same time, condensation control is something to consider as well. I assume some basic ideas remain transferable ... hth - good luck in your quest.