I have been asking that question since ...
Since the core is very close, try polishing up the Blue Heat IN SMALL INCREMENTS, with the same drilling as your friends.
That core is a great one, better, in my opinion, than the Elite/Slash/CrunchTime core. It was used in the Assassin, Money. Heat 2, Heat 2 Pearl, Enforcer, Sheer Havoc.
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Just like hand grenades and horse shoes, in bowling you only have to get close ...
CharlesT