IN THEORY, the core specs are very, very similar (good guess, Lonce!), but the covers are main difference. I've found PK 18 to handle slightly more oil than Super-Flex and be very SLIGHTLY stronger off the breakpoint, but Super-FLex skid/flips with the best of them. The covers are equivalent but not identical.
Hell, they're probably as close as you'll ever come to 2 balls from different manufacturers. Both covers last well and can be easily modified til the cows come home.

One good point is both are solid and not pearl.

I'd bet with minor cover prep, you can make them very close. Go for it!
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"We get old too fast, and too late, smart."

Lonce, I'm suring you were thinking what I wrote. ALthough it is trite knowledge, sometimes it just needs to be said/typed out loud, so to speak.
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"We get old too fast, and too late, smart."