I have been doing the same thing with my DD. She has some power, but was being taught more of a linear style with her upper body. Now that she's at a point where she can identify pitches and knows what to do with them we are adding rotation to her upper body with lower linear as described in previous posts. After watching the WCWS and seeing that almost every hitter (who wasn't a slapper) used a rotational upper body we decided to make the change. Getting a Zepp definitely helped, it gave some quantifiables to extra torque of upper body and showed DD immediate increased speed at contact without sacrificing hand speed. Rotational greatly improved her angles too. I found some excellent information on Hitting Performance Lab site. It's not really a formal program, but great information to build from and incorporate.
I was surprised at the push back I got from DD's hitting coach, team coach and others that rotational "show the numbers" hitting doesn't work in fastpitch and that "nobody hits like that". Obviously people who are just going by what they were told once upon a time and never really researched this even though its very evident watching college and pro players. We had to make a change in hitting coach as a result. Just to prove it, I went through each hitter in the WCWS championship game and took stills of their ready stance to load stance (all but one rotate upper body). I'd be happy to send you those images or post if you would like. Be prepared for push-back if you are going to try and implement team wide.
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