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.
