RE: repost: the life jacket problem
I use a Mustang inflatable vest. Very light and it does interfere with a seat harness - I'm not sure how it would work with a waist harness.
I've seen the kingston guys use the mustang inflatable pack attached to their waist harnesses. You can buy mustangs at any canadian tire.
Remember, in Canada, big brother tells you that you must wear a life jacket or be fined something like $100.