I had two heads laid out side by side in my garage tonight to compare ports and chambers. One being a Y8 and the other a Z6. The Y8's divider is set further back in the head than the Z6 divider is. I know the Y8's divider is curved for better economy, so does the divider location have to do with this as well? Also the Y8's divider could be described as a fat roll, while the Z6's divider is a supermodels arm.