I've found that there is another element of the question not yet discussed. Specifically, it applies if one is talking about stock length on a rifle with a peep sight mounted on the rear of the receiver such as an M1 Garand, M1 Carbine, M1A, AR-15, AR-10, Mini-14, etc. With those rifles and using the iron sights rather than a scope, it is important to get one's eye close up to the rear peep sight so the LOP isn't as important as the Heel to Aperture (HtA) distance (the distance from the top of the buttplate to the rear peep sight aperture).
I've found that my M1 Garand, M1 Carbine, and M1A, all came stock with a HtA distance of 14" while their LOP was 13". They were easy and natural to get one's eye up close to the rear aperture. My 583 Series wood stocked, Mini-14 Ranch Rifle came with an LOP of 13.5" but a HtA distance of 15.5" which required that I stretch my neck uncomfortably to get my eye in the same position as with the GI rifles it was supposedly patterned after. The solution was to add an aftermarket rear sight which moved the aperture back 1/2" and then cut the stock down 1" to gain the 14" HtA. This resulted in an LOP of 12.5" but the same sighting position as the Mil rifles.