As I stated adding holes and a x-hole will get you close.  Close enough that the cover easily does the rest. A 1"x3.5" x-hole can easily increase the int diff of a symmetric core ball to more then that of many premium asymmetric cored balls. 

I have a Sling shot currently with a 4.25" pin to pap and a large p3 x-hole and that ball will hook every bit as much as its 1997 counterpart the Sapphire zone. Same covers, different cores. The core will have an affect on ball shpae no doubt but if you get the rg and diffs in the same ball park you will see thst the differences aren't as clear on the lanes.

Nope but it shows how some of the things people get so hung up over such as static weights, pin distances and ect are not as big of a factor as the surface adjustments are.