I'm in the process of putting an engine back together too - please post your notes when you find them, hole size and number - I think thats a brilliant answer to the problem of crud jambing the plunger. I bought a ball bearing and spring but have been holding off installing them as several people have mentioned the same problem of seat damage with the steel ball.

I recently talked to keith calver about this. He says that the ball can vibrate and make the where it seats oblong over time. He does not run the ball anymore. Instead, he runs a modified plunger. id have to look through my notes but I believe you drill out 3, 10-12mm holes  equidistant from each other around the skirt. This allows antrying that could normally clog it, pass through. I just pulled out my plunger so I caN give this mod a shot. 

I too shortened the spring after I went to a ball bearing. Somebody smarter than me said add a washer or 2 under the plug instead. 100psi is too high IMO. The ball bearing won't sieze if some swarf goes through. I've a the bullet plunger sieze up a couple of times.

Ball is OK IF the spring doesn't bend and flick the ball off its seat. When this happens (often after a cold start), you get 10-20psi.
I cut a bit of 8mm steel bar 40mm long and put inside the spring. This keeps it straight, and still allows enough room for the ball to lift.

I'd trim the spring length a little to keep cold pressure below 100psi... but put the cut end OUTWARDS, away from the ball.

On my Spi car I had changed out the aluminum oil relief plunger for the ball type a few years ago. My oil pressure cold is over 100psi. When warm and idling it's where it should be. So.... my question is, should I change back to the aluminum plunger or stick with the ball? I'm tempted to leave well enough alone since it doesn't go low on pressure and, the main thing, it doesn't leak. Any thoughts?