Jeff,
If you are referring to my project, the flats of the sides are parallel with the barrels because of the way I machined the tenon. So, I'll mount the stock against the flat side and pickup the original hole at the head of the stock and drill it to just past the point of where the head should be. Then I'll flip it around and find center that I've layed out and bore in from the back with a long endmill to slot the back as per the factory original and reveal the small bolt hole. Then counterbore from the back.
I used the Devcon "2 Ton" epoxy.
