I found that trying to screw in the ball end of the barbell for the PA modification was tedious and, while using Chaster, would risk a penalty for taking too long to lock up. So I made a sort of safety pin out of a paper clip. One end is just straight, to go through the two loops and my PA ring. There's a rouble loop made by wrapping the clip around needle-nose pliers, and at the other end a little hook. The loop provides good springiness. Fastening it is easy and fast, and once covered with a cage it's secure. Here's a photo of my second prototype. I'm sure the little coil spring could be made prettier, and correct sizing of the spring and the hook would provide better clearance for the ring. (Alternatively, both parts of the clip could go through the ring.) I bet proper metallurgy could make a real spring out of better metal than "paper clip." If you don't want to fiddle with the barbell screws, give this a try.