No one think piston speed has a factor?????? Rpm is a relative term for valvetrain but for bottom end numbers I refer to piston speed.... So you have an engine that has the heaviest piston, and you want it to travel 9 inches (4.5 stroke) per RPM instead of 7ish inches(3.750) per rpm.

And .003ish piston to wall? every piston manufacture has there own specs that they send with the set....... because every piston will grow differently depending on the material they are built out off and bore size.