Just as a follow up I had my RH rudder lower bearing replaced recently.
, which was rather difficult it appears that the aluminum
outer bearing has corroded and seized the inner race
The shaft has then turned on the inner race
and worn to a large degree.
I think it would be a long while before it failed but the clunking noise
is rather annoying when you are try to sleep at night.
I also noticed that there is some crevice corrosion
starting on the shaft which I think will lead to shaft failure so I'm going to invest in some earthing leads.
This design is flawed and I will be looking at making up something like cat man do suggested as a permanent fix.