whitteaker,
Your are correct on the move to 43 ft. is a change. Kids must be willing to change the style sometimes when moving back 3 feet. My oldest was never a power pitcher but she could make the ball move. But in college with some changes to her curve ball, the 3 feet made it wicked. But, it nice to crank the 60 mph if you got it when needed.
As far as questions on Jennifer, Kat, Holly (8th graders) they can throw around 60 mph. But these girl have many more pitches then a fastball and to play at a high level of ball you must have more than a fastball only.
Speed is not everything. It also a head game!