If weight is enough of an issue that you want to use items of clothing for padding then why are you going for the extra weight of a surplus aluminum frame? If weight is not an issue then I guarantee you that foam padding will be more comfortable than using extra, and possibly wet, items of clothing. I would suggest that you check Quest Outfitters http://www.questoutfitters.com/patterns-packs-cart.htm#G-4%20ULTRALITE%20BACKPACK and look at the pattern and kit for a G-4 pack. It is roomy, light, and gives you the option of using clothes or foam padding for your shoulder straps and hip belt. It uses your sleeping pad as a "frame". I have made one and think it is a very good light weight pack. It will handle over 30 pounds if carefully packed and the price for pattern and kit is less than $40. Buying a kit for a field-tested pack is a lot simpler and cheaper than using trial and error to design a pack of your own. You can also get a kit for a somewhat smaller pack from Ray Jardine at http://www.rayjardine.com/ray-way/Backpack-Kit/index.htm. I have made one of these as well and found it to be a good kit.