azcat,

All nacra rudders and casting hardware were the same for that vintage and should allow you to adjust them so that the center of effort on the rudders gets right up to the pivot line of the gudgeon pins. It is entirely possible that the holes in your rudders for the pivoting points have been drilled in the wrong place. If your rudder head looks like other Nacras, I wouldn't go reshaping it. I would instead, find an opportunity to lay your rudder atop another known-to-be-good nacra rudder and compare the shape of the top and the pivot holes to figure out what difference is causing the problem.

Redrilling a pivot hole will be easy.