Eagle Creek EC Lync offers a convertible backpack + wheels for 4 lbs 9 oz - 22" size or 4 lbs 6 oz - 20" size. I believe that makes it almost 1.5 lbs lighter than other similar convertibles and it can be stored away in a bag. It is 1 lb 14 oz without the wheeled frame which keeps it on the lighter side for a 22" 43 L backpack, though probably not the lightest. It has the "No Matter What" warranty unlike the Load Warrior 22" which has the lesser coverage the lifetime warranty.

http://www.eaglecreek.com/eclync-system

http://www.rei.com/product/879699/ea...led-luggage-22

Interesting concept. It looks like the back of the bag doesn't have a stiffener and relies on the bar + frame? Could be useful as the fabric holding the single pole might allow a flatter back to the bag's interior.