Another CZ-3D question for Tom -

Can the CZ platform be tuned to minimize high tone falsing on nails, maybe at the expense of some other performance attribute?

You bet. Change the Grnd Bal settings for minimal falsing on nails. (((This procedure holds true with other units/brands also))). It's not perfect..... but has a fairly large effect.

So how would you set the grd balance? If I balance at 4.5 would I set it to 5.5? I know nugget hunters will set theirs to e.g 3.5 to gain some sensitivity.

This requires a bit of testing .... for your specific dirt/mineralization conditions. (Usually)...... you will find that 'lowering' the Grnd Balance helps the most. I have seen conditions whereby 'raising' the Grnd Bal settings helped...... but it is less common. In most of my applications....... lowering Grnd Bal.......... and by quite a bit............. is what is required to mitigate iron falsing.