This view shows the outlet opened up nearly as large as I will do it; but more importantly, it shows how #3 runner is redirecting the flow more upwards towards the middle of the plenum outlet.

This reshaping will reduce interference between runner flows because the flow is not aimed at the other side of the plenum now...into the flow from the other runners...but more towards the outlet opening. And you can "see" that the reshaping also works with the goilet now, instead of against it.