Maybe it's just me, but I've never been able to get comfortable with a back quiver. They always seems to slide down, and I can't reach the arrows when I go to grab one. I've made a few quivers from leather, tried lengthening and shortening the sling, but after walking around the quiver shifts so that my arrows are just out of reach.
I've settled for a pattern of back quiver that has a side draw and that seems to work for for range use, but I'd really like to use my piece of brain tanned hair on elk hide to make something more traditional.
I'm a skinny guy, and have always had issue with gear and harnesses not staying put, so maybe its just me?