Winter warmth

My GF was in the army and she still has her gear. She has these thermals that are very thin and keeps you warm. I forget what they're called. She says they're expensive but very useful.

I wear regular thermals under my jeans and shirt when I sleep.
Silkwieghts are the thin ones and Waffles are the thicker ones... wearing my old waffles now.
 
I just bought two kelty doublewide sleeping bags. Maybe give them a shot. It packs down HUGE so it takes a lot of space, but spread out your RTT may close on it.
I use the Kelty double in my cvt mt Shasta on top of an exped mat. Works wonderful
 
I pack sleeping bags an wool blankets. most of the time the wool stays down by our feet but if it gets cold we can pull it up. I've camped like this well below 0 degrees
 
For really cold nights I go with cheap thermals from Wal-Mart, a stocking cap and some good socks (not tight). I've made a DIY set of climashield quilts that pack down pretty well and are plenty warm. Most campers already know this, but when buying sleeping bags, consider their temperature rating as "You're probably not going to die at this temperature." It's never the comfortable, good night sleep temperature. If it's a brand manufactured for value over performance I would go with a minimum 20 degree buffer between expected temp and rating.