The pics are gone but Bruce aka Booster just marked with a pen and eyeballed it. I'd was afraid of the bit walking especially when held on an angle, and also whether I was aiming at the down passage. Vizard wrote Brad Urban's shop had a jig to do it. So way backwhen I sent my 3310-3 to QF to have it converted (Urban had sold or closed his shop and before Innovate had a forum). Eventually I got it back, but they hadn't been able to convert because the outer wall isn't thick enough on -3 to do it the normal way. In the long run I was glad they hadn't been able to make it 4-corner idle. My combos aren't radical enough to make good use of it.
