Getting worried-----

Careful drilling the hole in the PG, it loves to spider if the bit catches. :D

What I do is take a bit and shave off the sharp points right at the outer edge of the cutting edge, voila, nothing to catch now.

How do you plan to stop the piston in the exact same spot when going the opposite way? I suppose a fella could make one easy enough. The stop I posted is designed to be used with the heads off.