I wanted to be able to win more than one extra ball for each ball in play
via the captive balls on my 1974 Williams SKYLAB. The way the game is
designed, after you get all of the balls to the lit side and you get the
extra ball, the '5 balls in line' relay is 'held'. This makes it so that
neither side is lit and you can't win any more extra balls unless you get a
'Spacelab' special but the value for moving a ball to the other side is
increased to 1,000 points. All I did to my game is put a piece of a
business card between the hold contacts on the '5 balls in line relay'.
This makes it so that you can only get 1000 points for moving a ball to the
other side if you have the 'SPACELAB' letters all lit, but it flips the lit
side for an extra ball immediately to the other side which lets you get more
than one extra ball for each ball you play (if you can get all 5 to the
other side of course!).