I have recently purchased an under quilt protector from 2q2z and I'm in the process of trying to decide what to use as a vapor barrier. I must admit I'm somewhat skeptical having no experience with one. I don't like the thought of waking up soaking wet in the middle of winter.
Thanks for the information. This was helpful.
I think I'm going to try an Adventure Medical Kits S.O.L. Thermal Bivvy with mid/heavy weight base layer.