I worked with Ron Bell to develop a 4-oz EPIC vest that will accommodate up to four 80-oz Platypus water bottles (equivalent to 20 lbs of flotation), or three if you intend to use the backrest on your packraft. Should be useful in cutting some of the weight out of my pack during my upcoming Alaska-Yukon Expedition. He just went commercial with it:
Attached are some images of my home made “wine bladder” thing which we have been using for the last three years - the shell is made from 1.1oz ripstop, which enclose, through a zip in the lower seam, a 10l wine bladder at the front and another at the back. The bladder is folded to fit the shape of the vest. There are 2 x 1" webbing adjustable straps on each side, and a 1" webbing belt around the waist, to which things can be attached more securely.
The bladders are very useful for a pillow or water bag around camp.
The thing itself is also very useful if you want to look like a dickhead:
A comment on using your raincoat to hold bladders or air mattresses: I’ve done this; it can be done, but I urge caution: a friend of mine bailed with flotation stuffed under his rain coat, and the zipper blew out. He lost his flotation and almost drowned - so that tactic is only as good as the structural integrity of coat.