Last Friday night the temps got down to 30°F and I was very comfy in my WBBB. This was the coldest I've hung so far. I overprepared for the temps by wearing too many clothes. I had my baselayers, wool socks, Montbell Thermawrap, toboggan, and MH 20 degree down bag used as a top quilt. I woke up at 4:00 A.M. sweating and had to take layers off.
For bottom insulation I was using the GG 1/4" Wide evazote pad which is 40" wide. It fits perfectly in the BB, almost fitting seam to seam which makes it very easy to stay on during the night. It also covers my shoulders. The pad is only 60 inches long so I did have to have another section of pad under my feet (I'm 6'3").
All in all I think it's a really good option in a ccf pad. It insulates the shoulders, stays in place, and is very warm. Not UL at 11 oz, but not overly heavy either. Good piece of kit.