Dave: Hobie sells a retrofit kit to adjust your rudder rake.
(or at least the did)
You can change the feel some with the mast rake, but not enough to make the weather helm go away. I cut out the fixed stud on the upper casting and machined out the hole and then used a 5/16" ss nut and bolt as a way to rake the rudders on my old 14. It worked well. Drilling the rudders is also critical.We have a couple of guys with jigs around here that get a lot of business as people pick up new boats.
As was mentioned if someone has a boat with adjustable castings and are happy with thier helm you can use that as a starting point. I sailed an old boat last summer without the adjustable casting and an old set of lexan rudders. I don't know how we used to do that. The boat feels terrible. You have to put your weight way back and sheet out just to make the boat go without cavitation.