I have a new Rival that I want to have drilled to cover a medium to heavy medium condition (38 to 40 foot pattern) and give me a strong back-end.  What would be the best way to drill this ball for a senior bowler with slower speed and lower revs.?  The Columbia sheet shows two drilllings with a pin to pap distance of 4 1/2" and the pin placed over or under the ring finger.  Would this be as strong as placing the pin 3 3/8" from the pap and having it even with the ring finger?  If it helps, my A game is usually from 5 to 15 at the arrows either straight up the boards or with a slight swing.  

Any input would be appreciated.

With the slower ball speed, you'll definitely want to use a drill to get you length and you might need to add a little polish.  Definitely a Pin High drill, because of the lower RG this ball rolls in the midlane and is more of a strong arc on the backend.   Just like pate08 said, if you drill it too strong it'll start up too soon and die on backend, leaving alot of flat 10s or worse.