Having spent longer than I expected learning how to sail reasonably well, I discovered that many of my problems with boat handling could be directly attributed to poor sail trim. Add to that my positive loathing for sailing dead downwind, and I have become a nagging advocate of trying EVERYTHING before making any physical modifications to a boat.
We had such a terrible weather helm that I was exhausted sailing between islands in the Caribbean. One "expert" told us we needed to modify our rudder, but fortunately a friend who was also a circumnavigator overheard that conversation and suggested that we work a bit harder at perfecting our sail trim capabilities first. Good advice.
When I did more reading about How to Sail (with an emphasis on sail trim) we started experimenting with sail trim and various reef positions. We found that easing the jib sheet could increase speed and make the helm so easy to handle that I could steer with my big toe (TRUE!) leaving both hands free for talking and keeping my water jug handy.
Struggling with a full main going to weather, barely moving, it seemed, we were shamed when we were passed by a boat with two reefs in her main. !!!!!! Peter grumbled a bit, but he reefed the main and we gained two knots immediately. A few more tweaks and we started to overtake that upstart!
I did a lot of reading about downwind sailing since I hated the motion so much. I latched onto an article discussing the better technique of jibing down the rhumb line on a series of broad reaches. The somewhat longer distance was more than offset by the better speed and greater comfort of the reach. It took a major bribe to convince Peter to try this, but it took only one crossing to convince him. (the payoff of his favorite foods and no more whining from me might have helped, too
). In the Caribbean where the wind is so reliable, it was very easy to compare passage times when the only variable was sail trim.
Please experiment a bit more with sail trim before doing something as drastic as modifying the rudder.