Im pretty impressed with that game how many attempt till you got multiball? Just a small cheat install a stronger plunger spring and at full force the ball can bounce back into the top capture hole 
Well over a dozen games I think, I found if you play multiplayer you can achieve it easier.
The plunger spring is new and it works fine, the problem is the return thingymagig has lost its springback potential to flip the ball back to the capture hole.
