I checked your profile and you have slow speed. I wouldn't recommend a 4" pin. I'd stick closer to 5".
To answer your question, YES the placement of the MB has an effect on the shape of the breakpoint. To keep it simple, a MB close to the right side of your thumb will give you a longer and more snappy look. As the MB gets closer to the PAP the ball rolls earlier with a more controlled back end.
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Corey Clayton
Brunswick Amateur Staff
Turbo Grips Staff
Team Canada
Check out my arsenal in my profile.