Oh, as long as I'm rambling . .. . has anyone ever tried this? (we used to do this with the cheap DID clones . .. the screw on cap would never align the airhole). Put some sandpaper on a flat surface, and set the cap on it. Sand it a little (little circular motions, keeping it set firm and flat against the paper). Check to see where it spins to now. Sand some more, check, sand, check. You can probably get about 100-180° of airhole location adjustment just like that. don't forget, the airhole is gonna move clockwise, always seating a little further in the spin.
oh, we used to do that with the early AGA-Ts too, I think.