When its below freezing, I usually use my 5oz. Climashield XP quilts that my wife made. I always wear my mid-weight thermals and my wool socks to bed, and my windproof fleece with hood and a beanie. I keep very warm with this setup, and have been down to 15*F, sometimes I put my windshield reflector in too. I keep my tarp doors closed too. I really want to go to down, but its a want, I really do not need it for any reason. Climashield compresses well for synthetic, and when my quilt wears out, I will beg for down again .