[Paddlewise] PFD

Ive been using this water-skiing PFD for the summer and although not 
uncomfortable, it slides up and down which gets annoying.  Can you recommend 
a good PFD with flotation for a big guy like me.  Im 5'11 225 pounds.  I had 
looked at the lotus Rio Grande when I purchased my kayak, but didn't have 
enough $$ to finance it at the time.  Can anyone of my size tell me what they 
have?  Also, how many pounds of flotation is needed to keep me floating?  I 
used to be a beach lifeguard for my junior and senior year of high school, 
but I realize that when I need my PFD it will most likely be in a rough area 
where my swimming ability will not help such as me banging my head and 
knocking me out.  

Thanks for your time,
Tom
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