Lonely Planet's Thorn Tree travel forum, which after being shut down for a couple of weeks is now coming back to the net, might have better answers from a travel point of view.

Edit, later:Then, again, maybe not, because only a small number of sections on the LP Thorn Tree are up and the old posts are not yet there. There used to be a lot about backpacks used for travel. Do remember that airline baggage handlers are very hard on baggage, so a lightweight backpack, such as most of us here use for wilderness trekking, may not be the best solution for travel.