I'm thinking about modifying the game, since it's in poor shape and it's not an uncommon title. I'm toying with the idea of adding some kind of in-game bonus collect. Not sure where or how yet. I'd kind of like to do something along the lines of Bally games like Gator where you get a gate open and get the ball back into the shooter lane to collect. It'd be nice if I could tie it into the Newton's cradle, maybe you get all the balls to one side you get an extra ball and it turns on a self-holding relay, get the balls onto the other side from there, that relay keeps a path open to the bonus collect, which it does and then the self-holding relay releases and it goes back to awarding an extra ball. Just thinking outloud about it. I usually like things to be original, but this seems like a good candidate for trying something more.
Looking at the schematic, this seems doable. I really need to get the game working to know for sure, but I think I could rig it to collect bonus the second time you got the balls over. That would really change the dynamic of the game. I could see disabling the bonus advance from knocking the ball over to the other side, too. Then your advances have to come from the rollovers buttons, the gate at the top, and the rollover lanes. So you'd need to keep the ball up at the top to build up your bonus, then work the cradle to try to collect it during the ball. That might make it too hard.
I could see making the kickers do more, too. Add a ball return on the left side that's activated when the right side kicker is lit, and a save gate on the right side that's activated when you get in the left kicker when it's lit. Just a thought. That might be getting too complicated. If it will collect bonus in game with one added make break switch and a self-hold relay, that'd be good enough. I think it'd be better for it not to award double bonus that way. Then there is still value in building up your bonus before draining.