Excellent work Turgenev! Have a nice big slab of rep.

Regarding the slits, think of it this way. If you have the large end on the outside, when several dozen arrows come flying in they will all get channeled down into the narrow slit from which the defender is firing and thus increase the likelihood of getting hit. The reversing would only be necessary for more modern emplacement weapons that have fixed points, and you are not worried so much about large volumes of ammunition getting channeled as you are about being able to swivel to any angle.

EDIT: Never mind, I see that edgewaters beat me to it.