off topic (only a short note)

except Turnbull, there is - Karl F. Friday with two books on this matter. The first one is ''Samurai, Warfare and the State in Early Medieval Japan'' and the second one is ''Hired Swords: The Rise of Private Warrior Power in Early Japan''.
there is also one short discussion regarding this matter on e-budo forums: about swordsmanship

My opinion is that you simply have to make some sacrifices in regards to historical accuracy if you want to have enjoyable gameplay.