Hi,

Unless it is a formula or developmental class (such as Formula 18, A-class, C-class, etc), if you plan on racing in an "open" class using published handicaps (such as USSA Portsmouth, Texel, etc), then your boat MUST conform to the class for which it was rated. This includes sails, boards, etc. You might be able to switch some hardware, such as mainsheet blocks, but you definitely cannot use different boards, rudders, etc. (even if they are firberglass). The following statement was taken from:
http://www.ussailing.org/portsmouth/tables03/tables03mh.htm

"Ratings are based on boats being rigged in accordance with one-design class rules and with class sails and equipment."

Good luck with your project.

Steve Bellavia

P.S. I plan to make a pair of lighter and shorter boards for my FX-1 for pleasure sailing. This will have the added benefit of preserving my manufacturer supplied class boards for racing.