For backend, drill it with a lot of flare, but late roll. Something around a 4" pin to PAP and 3" above the midline should help the ball save a lot of energy. Put the mass bias in a strong position (3 3/8" to 4" from PAP). I'm by no means am an expert or even close to certified, so wait for the more knowledgable (ie. EXCALIBER, tenpinspro, etc.) to come and give advice before drilling it up!
--------------------
-Dino