On several Gordon Smith valves I have made, I left the ball free to rotate, and did not burnish or lap the seats. I did make the seats with the best finished cuts I could manage, and bought stainless balls with best surface finish and roundness that I could afford. Never a minute's trouble with the valves I have made. Good luck with yours,

I agree with Jeff in that a perfectly made seat should not need the ball to be tapped in. The problem is that you need a perfectly round hole that is dead square to the flat face portion. That means all done in one stage on the lathe and a reamed hole.

Yes, use stainless balls but you must use a 'throw away' steel one to tap the seat. There is no harm in striking a small tap. Use the balls and springs supplied by Polly.

You can't really burnish the seat because it is deep down inside the upper body.

The Gordon Smith designs should work superbly because, in the few designs of his that I have tried on 5" models, he has got the chamber in which the ball and guide sits just right so that coupled with the spring pressure they are a quiet and gentle semi-pop. Take care to get the ball seated in its guide EXACTLY to the depth specified.