Your class rules as published will make it difficult to get a PN rating as a group of boats... eg the F20NA class. You will be forced to calculate each boat individually because your class rule says min boat weight 320... which would lower your rating in PN, Texel or SCHRS and the owners would think this unfair since their boat actually weighs 420.

So that would force you to use the tables individually which is a PIA for all concerned.

You can create any class you want for the PN tables Historically boats like the CFR 20 and Poison Oak were one offs that had a rating in the table and so you can create a class for min boat weight of 390 and sail area equal to the existing N20 and create a descriptive name and go for it.. That would swallow all of the N20s and any of the customized N20's in the race. The provisional number would be phrfd to be a bit faster then the current N20. All you should need is the basic measurement limits and a letter requesting a provisional rating. Should take a week or so. sailors register and say they comply with the PN rating rule.

Alternatively, race under SHCRS or TEXEL and use the calculators to get your individual rating. Until the boat changes weight... all the N20 look a likes would rate the same.