I have one of the basic Ruddercraft replacements which has made a huge difference over the flat plate. After the rudder kept lifting part way I tightened it down as much as I dare lightly tapping the threaded arm with a hammer I happened to have on board. That has been working pretty well but I'm afraid to strip the bronze threads so I try to leave it once set. I'd like to be able to use a derlin pin, bolt, golf tee etc to keep it down but, if you snag a lobster bouy, the line rides up to the rudder casting without tripping the rudder and the rudder needs to be lifted by hand to clear it. Don't ask how I know. Maybe a derlin bolt combined with a hole just big enough to allow for removal on the water would make a workable hold down along with a smooth bottom paint like VC17.