All of what Rick said. You'll be wet no matter what you use but the prevalence of high volume cockpits makes the idea worth considering. I'm wondering if the rarity in it's use also makes solutions to it's problems less likely. Maybe heavy duty velco/tabs/buttons could be used to help hold it in place?
After playing with a plastic double in the surf I would think they would be bordering on a necessity for risky use as the amount of water is HUGE and impossible to get rid of compared to a single boat in rough conditions. It was hysterical trying to dump a fully flooded WS NorthStar plastic double at the beach. Couldn't do it with two guys. Could not roll it over.