http://rivendellmountainworks.com/index.html I have always been concerned with the ultralight materials vs. the AZ desert. I have been using a Rivendell Jensen. Super comfy, SUPER bomber (11oz cordura) and at 2lbs 3oz pretty friggin light. It's frameless and the inventor frequently turned cartwheels with the pack on to show how stable it is. Check out the classic Jensen pack sewn to order
http://rivendellmountainworks.com/index.html