The brass tube spacer looks like a good idea. But it caused me to wonder if there were any possibility of vibration (from speakers or whatever) making things rattle enough to cause any kind of electrical interference. I don't know whether it would be a rare or common issue or maybe even constant rattling spacers wouldn't make anything go screwy. I'm not shmart enough to know either way, just dumb enough with previous experience to ask in case it might.

Good job on the boards.

It is an interesting question and has some merit. Metal to metal in model aircraft and cars causes serious radio interference and is a no-no.

Whether there would be enough regular movement of the spacers in a pinball to create EMI is another matter? In any case, any electrical noise that 'might' be generated can't really do much - except perhaps upset your AM radio 

The board has been running fine in my BSD for nearly a week now and has worked flawlessly - I haven't noticed any side effects???