Hi Barry
There are three things I know of that go clunk in the 325/335 steering arrangements.
1 Loose rudder pivot bolt ( ours nearly fell out off the Channel Islands)
2 Wear in the rudder fittings, which was much improved by replacing 12mm bolts with 1/2" and I can't believe this involves any loss of strength.
3 There is some play in the steering mechanism itself on wheel steered boats. This would be really tricky to get rid of and probably not worth the effort.
I guess the important thing is that though the clonking is a pest it probably doesn't imply anything important amiss.
Martin
335/50