Create a separate team (i.e. USC Fall) to upload scrimmage stats into via Excel template, refresh in-game stats in another team (i.e. USC 2021), and then select “Merge Teams” > Merge USC Fall into USC 2021. Make sure players' names are spelled identically for the stats to merge.
There's no magic number, but we recommend at least 50 plate appearances. A better question is: Does the data I'm using for the simulation line up with how I think this player will perform?
Baserunning rates and fielding rates are specific to the sport and level of play. Softball also has a slap-hitting component, as these produce much different results in advancing baserunners than a non-slap hits. In conjunction with the user input statistics, these differences create completely different run scoring environments, each precise to the sport and level of play.
This is Bill James's "Speed Score" metric, a number 0-10 with 10 being the fastest. It's a weighted combination of Runs, Stolen Bases/Attempts, Triples, and double plays. The faster a runner, the more likely they will be to advance on the bases. It doesn't have to be perfect, just in the right ballpark.