Yeah, I made a quilt that (when used as an underquilt) gets me down to right around 30F, made with 2 layers of the 2.5 climashield xp. That was the lowest I got that underquilt before I started getting pretty cold. Cold sleeper though. I think we've established in another thread that you are too.
Using it as a top quilt, with a warmer UQ, I would think that you could get below 30F maybe.
So, I agree with Schneiderlein thatIf the combat is the 3.7 osy from thru-hiker, I would think a double layer should get you well below 30