I have been hand sewing my down TQ, I'll try to get some pics up when she's finished. Since it is being hand sewn, I have had lots of time to meditate on the design for my UQ...which i will also be hand sewing...after I finish the winter tarp. During my meditations I realized that the down in an UQ doesn't really do all that much to improve the efficiency of an UQ. On a TQ it is pushing the 2 layers of fabric apart to maintain the 1-3 inches of trapped airspace, and the trapped air is what is keeping us warm. But, on an UQ we have gravity working for us. In theory, with slight modifications, one could easily make an UQ shell that hangs with a relatively uniform space between the 2 layers of fabric and works just as a down filled one. The only real catch is that the shoulder area might need some help staying at optimal fluff.
My idea was to have the two layers of argon 90 with a 2 inch strip of webbing sewn between them around the perimeter (similar to the way baffles are generally sewn across the middle). Argon might work as the 2 inch strip, but I figure the stiffness will help it keep the 2 layers apart in the corners. Also, I would add a baffle (of any material) down the center (lengthwise) to keep the bottom layer from sagging too much. Everything else would be pretty standard, cinch cords on the head and foot, shock cord along the length for suspension, etc. I have also played around with the idea of having the top bit of fabric a few inches narrower than the lower fabric. The idea is that it would be easier to sew than darts, and should minimize compression (this is something I will mock-up once the rest of my fabric arrives).
For those that have months and years of UQ R&D experience under their belt, I challenge you to give me one good reason why I should put down in my UQ....other than the fact that I'll have 7 oz of the stuff left after I stuff my TQ. Thanks for the feed back.