Thanks edt, I think you mentioned about the ball not sitting straight before but I am trying to member what your solution for this was? Did you make your own stopper that would seat better in the ring?
i bought a big block of 1x1 nylon cut off an inch of it and drill a few holes like so
It's pretty simple doesn't need the red ball, o-ring, just a block of nylon and you are set. I also drill out the holes on the bottom so my flag out elastic line (which is as thick as a chicken line) wears a lot longer.
but like I said I haven't gotten around to converting my naish bar yet I still have that awful swivel. Got so many other projects I am working on, the above block is the one I use on my slingshot bar.