before reading anything on this forum, I actually made two with sewn footboxes. I've slept in a sleeping bag nightly for many years. When the "real" sleeping bag wasn't used, I used an old comforter sewn across the bottom and partway up the side. (with an old boot lace) I also made one similar from a wool blend "pendelton" type blanket bought in Mexico. The only other thing I did to the blanket one was fold a small hem around the top, and cut off the millions of "nose-ticklers". I still have and use both depending on the temp inside.
First the top quilt laid out flat. The draft stoppers are the black portions extending out to each side. In use, the draft stoppers are tucked under you.
Here's another with the foot box draw string pulled closed. The draft stoppers end up tucked under the legs and feet and hold everything closed and warm.
awesome looking quilt tired feet
Wear a field jacket liner over some real winter layers. Have an underquilt. Use a poncho liner as an over cover. Were a cap. Wool socks for the feet. It will get you through the night and you won't be burdened by heavy weight stuff. I've slept this way under freezing temperatures and stayed toasty all night. Go light. Good luck.