Thanks. This kind of design, V-stays, etc., seems to work well for me. I wouldn't characterize it as "heavy" though, since it weighs about the same as a ULA Circuit, and the lighter one (not shown in the picture, but similar design) is even less. Certainly not down in the Zpacks category, though.

I've never used Cuben fiber. It's pretty expensive, and I'm frankly not sure it's worth it for a backpack.

You said that the weight would be "almost totally down to the use of Cordura." Well, not really. The back panel made of 330d Cordura weighs about 1.5 ounces, and the pack bottom is slightly less. The Cordura weighs 5.73oz/sq.yd. There are a few other small pieces, so probably less than 4oz total.

Nevertheless, I've been considering some lighter materials. The problem is that the Cordura needs only very minimal reinforcing in the areas where the shoulder straps attach and none where the hipbelt attaches. Any weight gain from using lighter material is eaten up by the necessary reinforcement fabric. Using 210d Oxford for the back panel saves about half an ounce. I'm trying to use what I already have, if that's not already obvious.

I guess I have time to think about it...I made a rookie mistake on the shoulder straps and have to redo them.