In the Boyer article posted above he mentions how putting on an assymetrical trailing edge creates some pressure on the foils to fix the problem, I think it would be along the same idea. Mast rake and rudder rake will change the pressure on the foils too. It seemed to work for my rudders but maybe it was because I didn't have these things adjusted correctly at first, though the changes I made were not huge. The first thing I did was switch the sides the rudders were on just to see and it helped a little.