OK, I'm ALSO waiting for my WBBB 1.7 DL to arrive, and I'm starting to think about under insulation. Since I camp in areas where I may have to go to the ground I don't think an underquilt will ultimately work for me, so I was wondering how well a dual foam camp mat (in between the layers) would work.

Unlike CCF I don't think the dual foams are a vapor barrier so I'm guessing they would breathe, and since they're basically a sleeping mat I could take them to the ground if I had to...

Does anyone have any experience using these between the layers?