Thanks Sven-Olof. Strength is one consideration. Another is whether there is a change in orientation, stretchability, etc., at the spine that would cause the stretched leather to always show a line along the spine. This could be via a line of wrinkling, a line of puckering, etc. Just to clarify, I was going to split along the spine, not across the spine, i.e., a cut from neck to tail along the spine.