John,

I installed brass plugs in each fitting, and tapped 1/4-20 threads. I made the delrin piece to prevent any tilting. It was somewhat wiggley. It needed to go slightly over center to lock. To get it just right, the cap screw was installed and acts against the hex in side the delrin spacer. I get the balls to lock with a little gap. Once the balls are locked, the spacer/fitting is turned about 1/8 turn to close the space. Nothing moves after that. It does rotate.

I went this morning to try it at the beach. Then disaster struk. Both dogs found dead seals and were rolling and rolling.

No pelicans again. Must have been my lucky day.

Rich