The Jardine style quilt is very easy to make, but use 3 layers of 3 oz 3D (Outdoor Wilderness Fabrics). Jardine recommends one or two layers if I remember right, and that just won't do what I hear you saying you need. What I do is stitch one layer of 3D to each shell (the top and the bottom), lay another layer over the bottom bat, but stopping it about 8 inches from the edge which tucks under anyway, and where the extra insulation isn't needed, then run loose lines of thread between the insulation bats along the edges and down the length at about 12 inch intervals. Jardine recommends point stabilizing 3D through both shells with yarn ties. Get the directions to see what he recomments in Beyond Backpacking. I disagree with Ray and have not had good luck with the ties. I prefer to machine stitch short (4") lines through the bottom bat(s) and the bottom shell and separate stitch lines through the top bat and the top shell. I offset the stitch lines. 3D has the wonderful ability to cover quilting lines as long as fabric does not cover both sides of the bat; one side is OK. 3D fills in over the stitch lines. After quilting both sides of the quilt, stitch them together, isulation sides out, leaving a 12" gap. Turn the quilt right-side-out, close the gap and install whatever elastic, zipper, or velcro you want. That's it.
There are three easy fixes for the draft problem. 1) a bottom sheet zipped to both sides of the quilt, tapering to nothing but the zipper tape at the foot. Don't worry, there will be plenty of room. 2) Velcro matching Velcro glued to the sleeping pads. Every time you get up during the nite it sounds like major alimentary trouble, but does the job, sorta. 3) two adjustable elastic ties passing from the edges of the quilt under the sleeping pad to pull the edges under the pad. I have used all 3. The sheet works better for a double bag even in sub-freezing weather. The elastic works for a solo. I don't use the Velcro fix anymore.