Thanks for the feedback Firepower 
Interesting to see the comparison from another machine .
Of course there are variables such as
Condition of the PF , how often you wax, angle of playfield, how good (or crap) a player you are.
(Yeah I figured you guys would think I'm a crap player .. and I am  )
Far as I know freeplay mode shouldn't affect these stats.
I tend to aim for features too, especially multiball 
I didn't know about the max bonus issue (goes to show you how often I get it eh?) 
I have never got Special or Extra ball on this machine either.
I intend looking into the settings further to see if you can set parameters for achieving Special .. no doubt you can.
I'm pretty sure you can change settings so Extra ball is acheived from hitting the 3 power targets , but that ain't easy either, in fact nothing is easy on this game , but it sure keeps you coming back .
No doubt a great money maker in its day, I remember how popular it was in the arcades .
No wonder Williams made 17,000+ of them.

Cheers
Dave