I have used the Eagle in a hammock in a Scottish winter and the same bag in a snow trench in Arctic Sweden at -41, it worked well and the bags are very well designed, good luck with your search.
Should mean i dont get a cold bottom in a hammock in December in the UK Plus ive already got a great underquilt but have a feeling my little Vango Venom 200 wont be up to the job of anything below +4 even with the underquilt.
Hopefully one will turn up soon!
Since buying the snugpak underquilt i havent actually been out in REALLY cold temps but my Venom tends to get a bit chilly for me in the winter anyway, still, if i dont find the Nanok i may brave the cold without the upgrade
I have a snugpack SF 1 centre zip, -7 comfort -12 extre like new £100 posted.