I have a double (anti-backlash) nut (1605) that was removed from a ballscrew and the balls went everywhere. I think I rounded most of them up but who knows? In total I have 31, so say 5 per circuit. An actual circuit can hold about 10. It's possible they only populate about half when new, but I have no idea? It seems more would be better, and I can't see the downside to having more.

I have extra balls of the correct size in my collection, so I can populate more than the 31 originals that I found.

Does anyone have any insight on correct number and if there is any downside to having more vs. less?