If it will not stop reliably due to the rounding, your only option is to replace the bakelite disc or fabricate some kinda thing to make it the proper shape.

I think Phil H has a write-up on cdyn.com about mixer cams and fixing them. Similar process needed. You can probably cut one out of metal with a laser cutter.... Just a thought.

Would love to know what it is! Please post here once you have it going.

I spoke with Mike as well and he helped me understand that fix.

You have to cut out a new notch in the same area that it should stop normally, but higher up in the bakelite. So measure and mark, then cut.

Next you have to modify the coil bracket to slide the coil higher to catch in the notch.

Your fix will work for the rest of time, though!

Glad you got it working!