BMT; I'am not sure if this is the answer to your question but, it's a rule of thumb that I use. Try and simulate the clothing thickness that your most likely to be wearing for the majority of use to be seen by the rifle. In other words, a summer varmint rifle may have a longer LOP than a winter hunting rifle. That said, I prefer to have a rifle a little short on LOP rather than long on LOP. -memtb
