But the information I remember viewing discussed size relative to boat size. And most rudders are sub par. If for example any rudder even a correctly sized rudder is not engineered correctly then obviously there is a problem. And maybe (I'm only guessing here) designers are considering rudder size with the boat traveling at hull speed but when the boat is slower then the rudder size needs to increase to perform the same optimum function. Much like wings on a plane, a small slow plan needs much more area then a fast high speed plane to produce lift.

Ciao