I had the parts segregated in a chinette plate, a trick I haave use for planes for a while. What fell was a small hex nut. I found that immediately. That stop nut is how and where I found it.I would think I want the flat side on the bearing in the body.

Arrow, do I not have the standard rotor head on here? If not what is it?

I still haven't figured out how to balance this thing. Off to find instructions.

Tim