How about an ...."gasp"....EXTERNAL FRAME ? I regularly use an old Jansport external when i am the family sherpa and it only weights about 3.10 lbs with a 4500 cu. inch capacity. It's not very fashionable, but it carries great and is reliably comfortable. It has a bag bar shelf on top that you could lash a canister to, no problem. Lash your bag underneath in a waterproof stuff sack. Check out this smaller person model at Campmor :

http://www.campmor.com/webapp/wcs/stores...memberId=125002

Wish you luck in your search!

BF <img src="/forums/images/graemlins/grin.gif" alt="" />
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Hammockers aren't stuck up, they're just above it all.