2 weeks ago I did an overnight with my 8 y/o daughter and the temps went to 35 and it was raining all night. We both had CCF pads and she had a old -10 bag of mine and was obviously penty warm in that. I used my 3 season nest and besides my toes getting a bit chilly (just 1 pair wool socks), my body was plenty warm on top. I would say maybe another 10 or more degrees. I would bet with the ground sheet and whatever you use to keep of the ground, you could stay fairly warm. Just try an overnight in the yard to bail inside if needed.
On the ground issue, I only have 1 hammock at the moment and I can never refuse a night out with the kids....... :-)
Being the paranoid - I mean prepared type, I have an UQ but somehow I just don't feel right depending 100% on being able to hang. I usually carry at least my 1/4" JRB Torso pad. It weighs so little I have a hard time talking myself out of bringing it, since it is both supplemental insulation for the hammock and at least something for go-to-ground situations.