I am going to be buying a Henessy Expedition with the Supershelter. My question is this. . .would it not be more effective to use an unzipped 45 degree lightweight sleeping bag in the under cover rather than the open cell pad? I have one that is a 45-50 degree bag designed as a stand alone bag or liner for heavier systems.

Would not a sleeping bag do the same thing as an under quilt?