Having looked at the windsurfing rig and giving it a thumbs up have you considered using windsurfing race dagger boards for rudders, I've been sort of looking at them for my F16 as the trend is getting smaller and smaller surface areas as per the A class, the couple of old ones I have from older windsurf boards ( given to me from a local windsurf school ) are not quite big enough for the F16 but a smaller rigged 12ft'er, now that maybe a possibility + there are loads of these just laying around.