I shoot skeet and sporting from low gun. To decide LOP I shoulder the gun with my eyes closed while dressed as I would be when shooting. I expect the gun to be mounted with everything lined up when I open my eyes. If not then I figure out what needs changed to do that. The dynamics of the gun can change the needed LOP. My Guns range from 14 1/4" to 14 5/8" on the ones I shoot targets with. For the hunting guns 13 3/4" works best because I won't always have my feet set right when game shows up. 13 3/4" works best for the hunting rifles also. Everyones different, you need to experiment on yourself with different LOP's. My BT99 trapgun is 15 1/4" because it's pre-mounted, and I tend to prefer longer LOPs.