About the only 'sort of rule/guide' for piecing a back that I have - I try to avoid having a seam right in the center of the back - reason - supposedly it gets more stress with folding when it's in the center.
My reason - if it's 'way off center' - it looks planned - it it's 'almost on center, but not quite' - it looks like a goof-up to me. Also, if the fabric is such that seams are not obvious, I see no need to do the center panel with a strip on each side.