the adapter with the boss was used with a short silencer with a tapered section which helped align it
i have one some where along with a galway one
the biggest problem with them all inc the cnc'd ones that a lad made a year or so ago is that the legs on them that fit into the tube are much shorter than the original part
i did start to make some and have so far only made the plugs that go in the cylinder maybe this year i'll finish them