On the Nacra F18 the spi ratchet blocks are fixed on the outer side of the hulls, near the shroud adjusters. It is the factory setup.

Sometimes, mainly in small and medium wind I have a feeling it would be better to fix it on the inside part of the hulls, it would result a better spi shape. (performance spi, 2006). Also If I see the other models as Infusion, Capricorn, or even the Tiger or the Cirrus, all, mounted inside. I think these models also using the same cut spi.

Any suggestion ?