Just an observation: the nylon inserts on the lock nuts must suffer after years on the rudder. I noticed that the lock nuts do not stay "locked". Once there is play from loose bolts, the rudder casting holes develop side play and "require" re drilling with inserts to get the play out of the rudder. My first choice is to tighten up the lock nuts rather than re drilling and using inserts.
I now use real lock nuts below the originals to keep the bolts snug. Flat washers, silicon grease, and a little tension on the bolts. This will put off indefinitely, the real repair of re drilling and inserts. The bolts will remain vertical rather than crab sideways cutting the rudder casting. The keeping tension on the bolts takes the play out of the system if there is any original diameter left in the holes.