Actually, right before the end, Kettenburg built a small number of K-43's in both aluminum and glass, with spade rudders. It was a case of too little too late along with a still, higher price because they used the mahogany house and wood interior as always, not willing to compromise on quality. They also built one K-47 in aluminum.Rather surprizing that no one has copied the boat in. There is a constant quest for fast sailboats. I wonder how a modernized Kettleburg would do in an open ocean race against some of the modern GRP designs.
When the Cal 40 with it's spade rudder came out, the end was here for the K-boats. The designer (i forget who) later lamented causing the demise of boats like the Kettenburgs. He surmised that his boats had no soul....