+1 on combining another pad (zlite?) with the Neo Air.
The dome perignon is great warmth per weight, but a bomber style with shell will be warmer (covers ear, sides of face, a bit under your chin) and adding warmth to your head is always the lightest warmth you can add.
I can't explain the pysiology, but I know I feel cold, really cold, with a full bladder. I was always hesitant to get up and pee because I thought I'd get colder being outside, right? But after I've peed, I feel warmer and sleep better. It's surprising how much difference it makes. Thermodynamically, it makes no sense - that pint of pee was at 98.6F/37C already. But maybe there's something about a full bladder that turns down your metabolism? It sure makes a difference for me. So I now cut off the drinks 2-3 hours before bedtime, pee right before getting into bed and don't hesitate to brave the cold to relieve myself at 1 am.