The T foils AKA Stealth would be spot on, I think the Vortex actually had the same rudder ( 49ER )as the earlier Stealths, alas John doesn't build the older ones any more so you would need both rudders and stocks. Don't try and recreate the wheel, just buy a set as they are not that expensive if you put your time and development into the equation.

What do they do for the sailing, I'm not convinced they work quite as we think but slightly in a different manner, that of just calming things down a bit sufficiently giving enough time for the club racer to do something about the impending nose dive, ie turning downwind a bit to take the loading off the bow. For me its the noise the T foil start to make as you get a little bow down, its enough for you to start to think things are not happening as they should.

A lot of the more experianced skippers seem to feel though the T foils are just drag but if it avoids the dreaded time of swimming and righting the boat then I'll put up with a bit of drag.

There is another builder as well who regularly is on this forum S Barrett from Australia, if you are down that way then he maybe the port of call.