So, my boats (nacra 20) current rating is only valid as a one design?
If I wanted to change the area of all 3 sails and add beam, would it make for sense to have it measured and rated texel or SCHS(spelling) for the long run instead of basing off of a design that is very different from what it is today?
The short answer is no. I've only seen one race in the US use SCHRS and that was the Tybee 500. Mark S may use Texel in the NE but for the most part nobody uses either system in the US so your measurement cert wouldn't do anything for you.
Personally I think you'd have a ratings beater if you just took all the modifiers applicable in DPN. If there is a weekness/loophole in DPN it's in the modifiers which is the appeal of a frankenboat.