..and looking at the ring more carefully, I am not sure it will be strong enough with 2mm removed - there is not much metal to play with - regardless of which tool I use. hmm...
Yeah, that's what I'm worried about. Could it be this ring wasn't made for a crank with an 86 mm bcd spider? it sounds like it should mount with shoulder bolts threaded into holes in the arms of a crank with a larger bcd spider. Velobase is not working.