Building an arsenal will yield you many different opinions. I feel 4 balls is a perfect number for most bowlers. 1 for heavy, 2 for med, 1 for dry. With the 2 med balls have one drilled for control and the other for opening up the lane.
Well I have done an experimental arsenal that i'm using right now.
Heavy oil: Animal(pin 4 3/8 from pap, MB close to my VAL)
Med/heavy: Raw Hammer Doom(dulled 600 grit, stacked leverage)
Med oil: Raw Hammer Doom(box condition, 5.5" to pap above bridge, cg to 1oz and no balance hole).
dry: Raw Hammer Doom(polished with delayed reaction, 5.5" from pap above bridge, cg to 1oz and no balance hole)
I know most will think i'm nuts for using 3 of the same ball in my arsenal. I like it because it works well. Awesome ball and can cover many conditions with cover changes and layouts. The only thing I would change with what I have done is with the dry lane ball. I would drill it with the pin above but at 6" from pap. Other than that it's a great 4 ball arsenal for me.
The other way of looking at building an arsenal is with 6 balls. 3 balls for each amount of oil heavy, med, light all drilled lable. Then 3 balls covering the same amount of oil heavy, med and light all drilled with a power stacked layout. This 6 should cover all situations.
My personal opinion is 4 balls can cover almost anything most bowlers will face. This way all 4 balls will get some palying time and wont be boat anchors to carry around. Plus you really can eliminate over lap by only using 4.
