Very important to have faired hulls/foils. At the moth worlds the top guys were wet sanding their foils with 1200 every morning before racing. Because the foil is the only bit in the water, and due to the high speeds, any scratch can be felt through less than smooth ride and increased rooster tail off the foil which means lower speed.

On a cat with a long w/line length, there is a lot of turbulence so you don't feel these imperfections as much, but they are still there. So get out there and make sure the hull/foils are smooth! (Plus the boat looks better too)