My first boat was the 22' version of yours. When I got her, the rudder was missing, so I had a guy in Texas fabricate one. We had nothing but a couple of 'net pictures to go by, so the one he made was nothing near the factory's original. Matter of fact, I had him make it into a "kick-up" rudder, which might be another option for you to explore, and it seemed to work well. The 22', of course, had a transom hung rudder, which is different from yours, but the concept of the overall geometry is the same. Having said that, I don't think shortening yours will cause that much effect, at least not enough that it can't be compensated for. Now that I've gained some experience owning these things, I'd make my own, for whatever that's worth.