Get the AHPC stocks and lock down mechanism ( www.AHPC.com.au ) or similar ones made by www.catamaranparts.nl

I have the AHPC setup and I have none of the issue you write about. I tuned my rudders one two years ago and have not worked on them since. Next season I will have to replace the tape that secures the adjustment nutt but that is all. I warmly recommend these setups. Neither of them are very expensive. Catamaranparts can even make them to suit the width of your current rudders.

Wouter