i agree with 5 balls.
i dot understand why operators have their pins set to 3 ball.
when i owned a black knight (1980 WMS) and had it on site it was first set on 3 balls then after 3 months i set it to 5 balls and the money it took in doubled.
lets face it back then (1987) if someone put 40 cents in a pin and played 3 balls and most of them drained pretty quick they would stand there and think what a waste of my money i will go and play galaga for 40 cents at least i will get more time for my money. but when my pin was set at 5 balls per game, 40c for 1 game & $1 for 3 games i found a lot more $1 coins in it. sure it had paid out more free games but at least there was more coinage in my pocket at the end of each month.