[crakarjax]

I ended up grinding a small flat in the shaft and then drilling with a 5/8" masonry bit. I noticed in the process that I didn't need to sink the hole in the shaft at all on the sides because the locating pin sits flush with the seats as they slope upward -- I think grinding flats for locating would work just fine considering this, since a sunk hole is actually just removing material that doesn't need to be there. Using a cap screw might be a different story though depending on the head depth.