That IS an incredibly interesting idea. I love a Sunfish, that is one hot-rod little day boat.
But Lord the design "problems" that would dictate. Go fast sailing boat engineers/yacht designers spend millions on these plans, so making it truly very effective would be some trial and error. Now, I'm not for one second trying to dissuade you from it. Fact is, I would love to try it myself if I had the time. Sounds way cool. And I would like very much to see the finished design. And for the exception of that it wouldn't come back out the top like the factory dagger-board, (but so what, just haul it up until the wing touches the hull). If anybody doubts that it'll work, just look back when Conner took back the cup from the Aussie's. That year every boat but a couple came back at 'em with a wing.
By all means, I can see trying it. Shoot, maybe even a little ballast bulb on it too for a little more stability, hmmmm...