Hi again,
I just heard back from Steve Madden, at Madden Rigging (
http://www.maddenrigging.com/). He's been out on a delivery, as well as attending a Selden workshop. So there's a good start; riggers into actual sailing, as well as ongoing education tend to be much better than ones who aren't. He agreed that welding is a bad idea, and has the sources for the appropriate bushings, and I urge you to go speak with him. Let us know how it all comes out.
Fair leads,
Brion Toss