You've brought up another problem that is significant to Potters---broken rudders. With P-15 rudders (and maybe P-19 rudders, too; I don't know) they tend to break when water gets into the plywood cheeks of the rudder head where the pivot bolt goes through the rudder head and the rudder blade itself. Even though the outside of the rudder head is kept varnished, water can get into the plys along the pivot bolt.
When I purchased my gunter it came with a broken rudder. A friend fabricated a new rudder head and blade for me out of marine plywood and WEST epoxy. I bought bronze bushings to fit the thickness of the plywood and overbored the hole in the rudder head and the rudder blade. Then I took an elliptical rasp (on an electric drill) and made the holes bigger in the interior of each piece of wood. Then I epoxied the bushings into the rudder pieces so that the bolt will turn in the bushing and the epoxy will seal the bushing into the plywood. So far, it has worked.
Someone else on the Potter web (this is all in the archives a couple of years ago) suggested that the pivot bolt hole in the rudder pieces should be overbored and the complete hole filled with epoxy, which is then allowed to cure. Then bore the pivot hole out to fit the bolt, which would be in an epoxy bushing.
It would be better to make this modification, whichever variation you choose, before the plys get saturated with water and the whole assembly is weakened.
Rudder breaking because of water delaminating the plywood rudder is not a problem linited to Potters. It can happen to any boat with a plywood kick-up rudder. I know from personal experience of two ODay Daysailor 17's and two Southcoast 22's to which it happened. I was on one of the Southcoast 22's at the time that it happen--it was an experience that I wouldn't care to repeat.
Regards
Tom Grimes
P-14 #363 Far Horizon
Muncie, Indiana