Most of the dinghies I raced in college retained the rudder by means of a 1" x 4" or so strip of metal screwed flat to the transom between the two gudgeons, with the bottom 3" bent or "sprung" out away from the transom. this has the effect of trapping the bottom pintle down into the gudgeon. To remove rudder, simply press the metal piece flat against the transom so the pintle can slide clear.
Just a backup if the swinging L-bracket method doesn't work out for you.
Knowledge: Tomatoes are fruit.
Wisdom: Tomatoes do not belong in fruit salad.