This question may have been dodged,
1 fast Z, How much do you think the valves would have to move in order to make it worthwhile? a 3* difference isn't much movement at the top, but could move the valves over a fair bit, I think. Really, I'm trying to find ways to increase the total flow, and without moving the valves, I think we're just about out of new(rather, new to us) ideas.
Maybe I'm not paying full attention here??