[AtlUmpSteve]

Age is somewhat less important than the level of play. 14U rec ball will have a more liberal zone than quality 10A travel teams.

In any game with reasonable quality, I default to the NCAA definition, the entire ball below the top of the sternum. In a practical sense (albeit NOT politically correct), it seems pretty easy to visualize and set the top of the zone at the bottom of the bra, or where the bottom would be if she were wearing one.

With college coaches and showcases catering to that age already, I see no reason to call a different zone than what the higher level game demands. Pitchers need to understand that zone, batters need to establish that discipline.