The circular plastic shims work well. Murray's marine sells them. I'm not sure if Catsailor does. For recreational sailing I loosen the bolt where the rudder pivots slightly. This makes it easy to raise and lower. For a race I'll snug it up so that the rudder just barely falls under its' own weight while sitting on the beach. This makes it harder to raise and lower but it takes a lot of the slop out and improves helm response.