I couldn't open the Selden link.
I made a replacement to the gate illustrated and I have used that in conjunction with a previous modification (which enlarged the mast gate cut into the extrusion by 75%) wherby slugs are pressed through a flap. This doesn't work very well because clearnace to the aluminium wall in the extrusion is not deep enough. (The clearance is therefore too shallow for the flap fitting, which I can't now change, modify or copy).
Anyone renewed the rudder bearings or serviced them: any tips apart from digging a hole for the rudder to drop into?