You are right about the complexity of the system. Portsmouth is hard enough for some RC's without making it too much more complicated. However there is a definite need for a way to prevent the depreciation of the ratings as a boat is raced less over the years. In fact, one of our Fleet Members chose to race SC20 knowing of the advantage of the depreciating Portsmouths. To take further advantage, He has adapted a new Squaretop ARC22 mast/sailplan setup for his SC20 which gives him a minor Change in his DPN's but a huge advantage in performance which are NOT accurately reflected by the adjustment in his DPN's.
It would seem that DPN's depreciate with the aging of the boat. There ought to be a way to reinstate the DPN's back to the original rating when a Racer refurbishes his boat back to "New condition " performance standards.
Just my .02
CARY