Luiz,

the theorethical advantages of gybing boards are good, and the reasoning you and Tom have worked out is the same as the one described in some of Marchajs works. Asymmetrical foils looks even better. But they are too cumbersome in use for practical racing on most boats.
The NACRA Infusion F-18 have gybing boards, but as far as I have seen they have not dominated events (yet). If we can agree that talent (sic!) is fairly evenly spread on local events, the Infusions should be generally faster. Perhaps the F-18 is too heavy to showcase the advantage of gybing boards? Anyway, I agree with your reasoning, but still think the jury is out on wether they really make a boat faster.