I get some cavitation (sp?) in my boards when I get above about 8 knots of boat speed (that is a guess because I don't have a GPS to judge speed). The board just kind of hum. I like it because it lets me know I am staying at speed. I think the easiest way to get rid of it would be to put some indoor/outdoor carpet in the daggerboard wells at the front and back of the well. Just a little piece to hold the front and the back of the board stable would probably fix the problem.

Rob V.
Panama City
Nacra 5.2