Some years ago, this topic piqued my interest, so I began to measure the the length of pull of military rifles and muskets to see how they stacked up to modern ideas of rifle "fit." Every single military arm measured, ranging from an 1842 musket, 1863 rifle musket, 1884 trapdoor Springfield, 1903-A3 Springfield, Krag-Jorgensen rifle, M-14, and an M 16 A-1, all had lengths of pull of 13 inches to 13 1/4 inches. The amazing thing is, every single trooper, of every size and shape, from the 1840s to the Vietnam era could, and has shot millions of these old guns, quite effectively, with no problems.
IMHO, based on my research, the length of pull controversy is a non issue. Personally, I prefer nothing longer than 13 1/2 inches, though 13 inches is good too.
J.D.