I went to a couple of paddling shops and weighed all of the L/XL PFDs they had on display. My chest is 45" and so this is the size I weighed. I also measured the weight for a number of PFD sizes above and below L/XL. On average, there is about a .1 lb difference per size.
The MTI Livery PFD seems to be the best standard option for rough water packrafting at .9 lbs. This is only .06 lbs heavier than the SOS Scout inflatable suspenders before any modifications to lighten them. It has these additional benefits: it can be worn under a properly sized windshirt or rainwear for insulation, in lieu of a high loft vest; the two side straps and the accordion style foam on the sides allow a comfortable athletic fit for paddling; and there is an elastic safety loop that locks the zipper in place.
I misspoke relative to the Astral Kapok (natural material) PFDs. Contrary to the marketing hype I read, they weren't lighter than the comparable PFDs with foam… sorry Roman.
I am sure that a custom PFD could be created that weighs less than the MTI Livery but, the safety tolerance would probably be lower.
