My '65 7ECA has one, and it greatly reduces the need for holding right rudder in flight and during the takeoff/climb portions of flight. It's roughly a 5-inch rounded (oval) shape that extends about 1" past the trailing edge of the rudder at the middle of the tab, but is rounded so that the top and bottom edges of the oval are basically even with the trailing edge. No clue if that is "stock" or was added later on. (Though there is no log entry for an addition, so I suspect was installed at the Champion factory.