I am making a new quilt, but would like to combine bivy like aspects to it. I am thinking of putting a sil nylon bottom (rather than open with ties) with ties for a neo air pad or Med exped. The pad would become part of the quilt, kind of a hybrid top bag/bivy combo. I am trying to combine function of bivy for under tarp with the quilt avoiding carrying both and to keep it together at night. Any problems with this idea?

One more question. I am thinking of using some 1/8 closed cell foam for the bottom as a combo pad/groundcloth instead of just silnylon. Is that hard to sew/waterproof seams?

From my experience I've concluded that quilts are warmer when they are held close to my body. I used to want to attach the quit to the pad thinking that there'd be less heat loss due to drafts when I roll over but I seem warmer when using a quilt that is not attached to the pad and is free to be close to me.