I have very limited racing experience on Thistles. On our lake, the DS was recently a major racing class, but is now rarely seen. On some nights there might be a single DS.
In areas where there is only one boat, do the class rules really matter? Can't a heavily modified DS (bowsprit, nonstandard mast, UPS, etc.) race under some kind of handicap as if it is a one-of-a-kind boat?
My impression is that a lot of DS II owners treat their hulls the way cyclists treat their frames. Just like a particular road bike might have a Motobecane frame, Campy gears, Shimano brakes, etc., the DS II hull is a nice "blank" on which owners build their own sailboats. A DS II (and maybe even a new Cape Cod DS I with bulkhead and hatch) can't ever be competitive against an old stripped-down DS I, so why not take advantage of the DS II "cruising" features, and only race against your own handicap (or just for the fun of crashing into other boats at the start)?