have to admit, I've never had an issue with ball cups popping off...admitadly, I tend to race outdoors, or on a carpet track that uses sand filled hose, so rarely come across solid boards.
You could try the Hara tip of gently heating the ball cup over the ball joint (ball cup shrinks to the ball joint) or a very thin layer of CA glue inside the cup.
How old are the cups? and how often do you pop them off for maintence?
Popping the off the ball joint is the thing that wears them the most.... I now use the hexheaded ball nuts, with a hole drilled in the ball cup, so I never have to pop them off, just unscrew the ball joint.
HiH
Ed