Hey Brian. I had just enough insulation to complet the quilt with a 2 yard piece of the 3oz variety and I am pretty tall (6'2"). The reason that it worked even though the height is taller than the 6 feet of insulation is the extra fabric needed for drawstrings on top and bottom. I used a derivative of the design that Jeremy padgett came up with on the thru-hiker website
The new dimensions that I used are as follows:
82" total height, including leaving room for sewing
54" across the top b/c my shoulders are broad (you could save fabric and weight here if you wanted to cut the uninsulated bottom closer to the edge of your body when you lie down, but I prefer an extra ounce and zero chance of discomfort
30"from the bottom of the bag outline (the first image you see on the above link) to where the wings that will eventually make up the foot box.
If I were to sew another bag using this pattern (which I probably will because it has worked out so well, I'd probably shorten the 30 inch wide footbox that reults to 20", b/c I just don't think it's necessary to have that much footbox in a summer bag. The 10" of extra height on Jeremy's design is because you lose a lot of height when you cinch up the footbox. I finished this bag with 5 yards of momentum and there is no bottom seam. I cut out one side of my pattern, then folded it over the bottom edge and traced in onto the other side. Thanks for the kind comments!