As a former machinist and toolmaker, I find it very difficult to accept hand filing of the "hook" which is the bearing of the barrels. While I believe it is possible to file a welded up hook to fit well on the hingepin, I think it is more likely that small contact area is the result leading to premature looseness (off face). I believe this is a job for a jig boring machine to ensure full bearing of the contact surfaces. JMO.

BTW, my BSS has a replaceable pin between 2 endcaps which are screwed in, then the slotted head is filed off to blend with the frame and engraved. Replacing the pin means replacing the caps, but it's still better than some other systems.