For me and my son's sleep system we had a Mountain Smith Morrison double wall 2 man tent, we left the fly hang down to keep more heat in.
I was in a Borahgear silnylon bivy with a 20* over stuff EE Tim Marshall quilt, and a syn. over quilt that I made out of Nobul 1, Ripstop nylon from Joanns and 2.5 Apex for insulation inbetween, on top of a Neoair, an emergency blanket that my son brought was under the Neoairs to reflect heat back to our bodies.
My son was using the other EE quilt that was a 0*, he had to strip off clothes in the middle of the night, he said he was uncomfortable and hot, that was untill the quilt became untucked from the pad, then he said he could feel cold drafts, his feet got a little cold also, but that was due to not shifting more down towards his feet.
To be fair though, when we went to bed, and after restling around with all the gear we generated a lot ou btu's, and the temp inside before we went to sleep was a balmy 48*,
Later that night I wanted to check the temps, and as I unzipped my bivy I noticed it was soaked, it was totaly wet between the syn over quilt that I had made and the bivy, but the down quilt was completely dry and warm next to my body, that proved one point I wanted to try out, and that was to see if the over quilt would soak up the condensation and still keep the down quilt dry, plus add a few more degrees to my sleep system for little weight gain, success! I never got cold at all, the final low temp in our tent was 21*, it may have got lower, but out of all the times I checked that was the lowest reading.
Overall I was impressed with my new over quilt and will make another one that weighs a little less to take on future winter trips, not so much for the added warmth, but more for the condensation barrier.
I also wore silk base layer top and bottoms under my Merino wool base layer top and bottoms. Then for my feet I wore merino wool socks inside my goose feet down booties and foot warmers on my socks and between the booties.
We did create a lot of condensation inside the tent being that there was two bodies exhaling all night, most of it froze to the tent, but a lot was inside our bivy's from keeping our heads tucked inside the quilts. I also was wearing one of Kats beanies, those things really work well.