@
wizard: No worries, frankly I deserve it. I have successfully replaced a thread once before - wall anchor/plate securing heavy gym equipment in a basement gym - which gave me false confidence. I was really dumb not to consider that I might be weakening the frame, and that drilling into an irregularly shaped frame is harder than working on a concrete floor. Plus I could have paid ten bucks for a seat post bracket for the rear rack.
So yeah, feel free to hold me up as an example not to do this.
Getting back to the repair: I don't feel the need to get another thread in there, although I'm not opposed to it. I just want to make sure that the frame is as strong as possible and I won't have a catastrophic failure. Seems like a (still relatively small) hole in that part of the seat stay *shouldn't* be a big risk but I've already FUBAR'd this so I'm seeking help here.
BTW, I've tried to find help from frame builders and machinists near me and they're all slammed, either can't do it or not returning my call.
So thanks and yes for the third time I'm an idiot.