Tim Marshall's enLIGHTened equipment has been added to my Cottage Gear Makers list (at side bar).
Tim makes quilts high-quality insulation and shell materials, including 800+ down and Momentum 90. He also does custom work. He has also pioneered the use of 0.33 oz/yd^2 Cuben fiber in quilts, and has developed the so-called "World's Lightest Quilt" (WLQ), which he has named the Epiphany. Steve Evans of BPL got the original version, the WLQ-1, which uses 8 oz of 800+ down and weighs in at a paltry 11.01 oz. The link is to the now-lengthy forum thread about the quilt, its subsequent models and other ramblings. Tim's custom work has included making synthetic quilts for a child and toddler, which he did for BPL staff member Doug Johnson.
Tim's site also includes a downloadable Excel spreadsheet whereby you can get a good guess as to how much your custom beauty will weigh.
You can contact Tim via e-mail.