Formula to shave pistons to reduce compression ??

Not cam timing cam specs....................lobe overlap can effect compression.
Cam timing, overlap, lobe speration, etc. all have an effect on cranking compression, and dynamic (running engine) compression.
But static compression ratio is determined by piston, cylinder heads and gaskets. A static compression ratio of 10 to 1, will be 10 to 1 whether its got a 210° cam, or a 320° cam.