Pitch is the foundation of the stock on the body. How you perceive recoil and cheek slap depends on pitch. It also influences barrel rise on recoil and recovery for the second shot. For these reasons it seems to be as important as other dimensions.

I have come across three ways to measure pitch: as an angle in degrees of the butt to the line of sight, by the floor and wall method and by measuring from trigger to toe and heel. The last one seems the easiest to do and record.