Even though 2618 is pretty common for forged pistons, the internal shape of pin bosses, struts to the skirt, inside dome arch, etc. all affect how the piston expands so the manufacturer gets the last word (but must always have all details including fuel, cooling etc.).
The penalty for guessing wrong is pretty expensive; a piston made the wrong shape (not enough/too much cam or barrel) can't be completely fixed by adding clearance, the entire profile should be re-machined.
We just through this when a piston made to the stock contours (but CD changed for stroke length) seized on the pin axis by less than .002" (not enough cam). It can be cured better by hand with a file than honing the cylinder +.002".
We had all existing stock re-done.
