I researched this some and basically it depends on who you race and the race committee. When there is not an accepted modification to PN for a given modification then the RC can make one up. Or if the guys you race with don’t care then they leave it alone. I would make it an A boat and make it as light as you can. (You can look up their rules. good "class" to be creative in). The bottom line is that PN #'s are averages of like boats and unless there is a bunch of people with the same mod it never gets an accepted number so the RC makes it up. And as you can tell you can not do anything except replace a part and be "class legal"
my $.02