Your plane of sight. from your peep to the end of your sight pin to the target. i wish i could draw it on here but basically its the same concept as a longer stabilizer. the equilibrium of the balance between eye and sight and sight and target are the factors. so, eye/peep-sightpin-target. the sight pin is the median, but it is offset on your to your eye side. the closer you get the pin to the target, or further away from your eye, the more fine your accuracy will be, b/c of your perception of the pin. hence your shooting "should" become/be with an extended sight. but everyone hasa different preference as well with their extensions so it is debatable to how far is perfect.

its hard for me to explain on here without using an equation, so if anyone can simplify this please do. and correctme if im wrong PLEASEbut i think i have a good ideal going here. but im sure my theory can and will be debated so...
Derek