I'm going on a trip this weekend where the lows will be around 30 degrees. I have a 40 degree 800 fill bag that I feel good down to about 32 in the backyard. I'll be using a WBRR and 20 degree Lynx. Will the 40 degree bag used as a quilt go down lower since the whole circumference will be bunched up on the top?

I also have a 15 degree down bag but it is 600 fill. I'm debating taking extra clothes and the 40 bag or just the 15 bag. I only have so much room in my pack. I should probably just be safe and take the 15 but I'm still curious.

And BTW, I won't have this problem as soon as my 20 degree Burrow comes in.