Well, like I said, they don't just slide right in. the attached pic should explain it alot better than my fumbling words about the screen can do.
Dwyer has the same dimensions on the outside but a drastically differing profile or shape. Our extrusions have a teardrop shape while theirs have an almost perfect eliptical outside profile.
So while I shaved off the shoulders a bit I'll have to build up the sides to give a snug fit inside the boom. That fit is what, I believe, will give it strength at the union between the boom and the new pieces. That will be more evident when I get to the outhaul fitting where it will have even less material left after the file. I keep picturing it 'flipping' out of the boom end and shooting toward the mast head. How will I ever overcome that?