so the pivot point remains constant which gives you a longer righting arm, basically you get the boat weight and a small increase in arm length. Neither of which is insignificant in such a light boat. If I'm reading this right, you'd get a similar effect in a traditional hull where the freeboard was the same height as the vertical foil length and the vertical shape of the hull was concave if you were able to heal to windward (this would suck for other reasons.) So nothing intrinsic with foils, just you have the limit condition for a concave hull shape.
Have any comparisons been performed foiled moth vs. windsurfer with the same sail area? It would be interesting to compare as the records would seem to indicate that the foil boat is not as efficient.
