I recently got my WBBB and Hammock Gear 40* Incubator. I slept very comfortably in this setup the past two nights at about 39* and 37* for a low.
At first I was worried about the area near my feet being covered, but I just pulled that cord tight closest to my right foot like Shug suggested in a video. This worked great, absolutely no need to any mods in my situation. It may depend on your height or lay position in the hammock.