According to what you're saying, I would probably put the pin right by the ring and/or a little up. I don't think this is the best lay out for you, but considering the ball has a 4.5" pin, you don't have many options.
The layout that you're looking for would be pin below the bridge. Pin below the bridge would get the ball to start rolling early, but keeping the distance to the PAP at a reasonable amount to keep the back end reaction. Make sure that the mass bias stays close to the thumb too.
If the ball is going to need a balance hole, make sure that you're driller doesn't drill it too close to the pin. 4-5" should be fine. Since you have a long pin, most likely the balance hole will be low, which helps you out.
Hope this helped, let us know how it goes too!
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Edgar Atienza
Roto Grip Staffer
Manager of Best Bowling Pro Shops - Plaza Lanes, St. Charles, MO
edgar@bestbowlingproshops.com