On my Godzilla machine, the balls fly out of the Godzilla head from a decent height and at speed.
It's never caused a dimple or hassle on the Playfield ever and the flying balls happen a lot.

The game is a Sega 1998/1999 title in great condition so I don't see the balls coming out of the KISS machine being a issue at all. The Stern playfields are pretty tuff. Just like the cannon launched balls on ACDC titles, haven't seen any hassles on my ACDC machine or anyone else's ACDC machine either.

Change the balls before pitting or rust sets in and I think like the Godzilla machine, 16 years later, not a hassle to be seen.