if any of you remember CB spinners
I ran the CB metal spinners on some early Formula One engines. They were unbalanced crap too due to the fact that they were cast cones. Because of the dynamics of rotating bodies, balancing a spinner is practically impossible to do with the tools available to the average hobbiest.
The CB spinner put too much strain on the bolt holding the cone to the adapter because of it inherent unbalance, and eventually it would snap and another spinner cone would depart the airplane. Examination of the remain piece of bolt showed that it work harden, developed a crack and fail. After loosing a couple I found that the only way I could avoid this was to change out the bolt after every 10 flights.
However Tru-Turn spinners run with very little stress on the bolt. I once started a racing engine with the center screw loose, and the Tru-Turn cone stayed completely in the backplate groove and ran without any pressure from the screw to hold the cone in place.