My rudder was loose on the shaft, it had a good amount of movement and I was concerned it might fall off of the shaft. I did read a post somewhere that someone did have the rudder fall off, while at speed. Pretty scary ride. I never found any posts about fixing this issue, so here is my repair. I found a machine shop that could weld the rudder to the stainless shaft. He drilled two holes on each side of the rudder until the holes met the shaft. Then welded the rudder to the shaft, and filled the holes in flush. Also ran a weld around the shaft at the top of the rudder.
Don't know how other rudders are made, but my Boomerang rudder had two bronze pins holding the rudder to the shaft. Bronze is probably a little too soft for this application, at least it was on mine. This might be something we all should keep an eye on.
Can't upload the picture, but it is my profile pic.