centreboards

Never used one, but my gut instinct would be to be very suspicious. The type of boats which use them (say 505s for example) would plane upwind in any decent breeze. In these conditions, you would be putting the bow down to generate speed and would be tacking through more than 90 degrees. The windier it gets, the lower a planing boat will go upwind. Height is secondary to going fast, and it often seems that height is obtained by going fast, so why have the extra drag of an angled centreboard?

On the other hand, it often seems to be the case in sailing that something just seems to work, even if you can't quite put your finger on why, so who knows?

Because you have to have it anyway, you don't have a choice. Your centreboard needs an angle of attact to generate lift; this is why all boats with symmetrical foils have a certain amount of leeway, and also why you go sideways if you stall your foils out on the start line. If your foils are inefficient (eg a bilge-keel cruising boat) your leeway could be shocking; with modern high-performance foils on a fast dinghy it should only be a few degrees. Nevertheless, your board is angled slightly off the direction of travel, that's how it works. The concept of the gybing board is merely to point the hull in the direction of travel so that it's just the foil going sideways, not the whole boat.

I suspect the reason that gybing boards aren't universally used is either that the extra drag of a non-gybing system isn't that large, or else Jim's argument that you may not want to run the rudder in the wake of the board.

When I sailed 505s, gybing boards were all the rage (they stopped gybing when you pulled them up to go downhill) but maybe that was a fashion thing; the boats I sail now have daggerboards, and I'm not aware of anyone having even tried a gybing board.

Dave