Realised my DF65 was turning wider to Starboard than Port so needed to change the end points to set the rudder movement the same in either direction. Created this simple tool. It slips in to the rudder pivot, lines up with the backstay attachment and then held in place temporarily by a piece of tape. Allows you to set the rudder angle the same both sides. The marks are for 30, 35, 40 and 45 degrees.
The model is only three 0.2 layers thick - colour change for the last layer.