Selden boom sheave relocation

[sean c]

On my Bavaria 47C I have in-mast furling. Unfurling the sail requires use of the winch after there is any tension on the outhaul line in the cockpit. No wind load on the sail.
I have lubricated the sheaves in this system and all seems free. I stand up next to the mast to assist the sail out and all is free up stairs.
The only issue I can see is the sheave on the mast end of the boom is in the centre of five sheave slots and is rubbing a wear mark on the side of the end fitting. The line does a sharp turn to the next sheave on the Port side of the mast. The line appears to be riding up to the top of the sheave where the wear mark is instead of sitting in the valley of the sheave.
I am considering moving the sheave from the centre slot to the first slot on the Port side to reduce the angle for the line and get it to run on the sheave instead of riding up like it does now.
To do this I would need to remove the 'Retaining plugs' (Item 6 on the drawing), knock the 'pin' out and relocate the sheave and put it back together.
I tried removing the retaining plug with an Allen key thinking it has a hex head. The hex head appears to be tapered and this was unsuccessful. I don't know how they are removed.
Any help appreciated on how to remove the retaining plugs.
Sean

[Yngmar]

Seeing how bad the shaft looks, your problem is probably going to be revealed when you remove the sheave: The crusty shaft has eaten the center of the sheave and it's now oval, meaning it turns when tested with no load but poorly when loaded. Had a similar problem on our outhaul, although different boom end fittings.

The plug will have to come out to remove the shaft, so get to work on it. I doubt it's supposed to be tapered, probably someone already battled with it. Can cut a groove in it and try that, or drill it away and replace plug and shaft (shaft probably needs replacing anyways).