What is the minimum class crew weight for the Nacra F-18? I know what the NAF 18 rules are, but when racing non-NAF 18 in a portsmouth fleet (i.e. the Alter Cup Qualifier) what is the minimum weight to use the 63.5 DPN rating? When you go to Performance Cats website and click on Nacra Class rules, there aren't any rules written for the Nacra F-18. The Hobie Class rules have the Tiger min. weight at 308.