So far I've got 8 cards for games with settings for 8 balls minimum.
All Gottlieb games.
Astro, Batter-Up, Dimension, Fun Park, Melody, Mini Pool, Palace Guard and Pop-A-Card.
For Hearts And Spades I've only got the 3 Balls minimum card (back and front).
Please send me a scan of the 8 balls version too and if you have it, the 5 balls version.

Peter
www.inkochnito.nl
inkochnito at kpnplanet dot nl

There are a few more I think.
I did a search for "minimum" on my website and the following games came up:
Astro
Bank Shot
Batter-Up
Card Trix
Dimension
Flipper
Flipper Clown
Flipper Parade
Fun Park
Hearts and Spades
Jungle King
Mini Pool
Neptune
Palace Guard
Pin Up
Pop-A-Card
Rancho
Rock Star
Ship Ahoy
* Team One (3 and 5 balls only)
World Series

For most of them I've only got the 3 and 5 balls version.

Is there anything on the back side?

I guess we can take this one of the list.
Too bad I don't have any of the schematics for these games....

I did a search on the ipdb for Add-a-Ball games and a very long list came up.
Filtering to Gottlieb only revealed 89 games.
Not all of them have 8 balls minimum, but a lot of them have up to "10 balls to play" on their backglass.