one correction is the current Nacra rules are located at Nacra Class I saw a modified 5.5 sailing on a Lake in Madison, Wi. Motored over to the owner, boat was a 5.5uni with carbon mast, special light rudders, & large jib ( I think it was a new 5.8na jib)boat was modified by the Nacra dealer.
There's a post on the old forum by Carl, he talks about another Modified 6.0 called the Cathouse 6.0/20
fair winds
Ted