I'm not a porter so forgive me if I've got this totally wrong. It is my understanding that more flow does not automatically mean more velocity. Think about a garden hose with the water flowing out freely, this has the greatest unrestricted flow but it does not shoot out very fast. But put your thumb over the end to add some restriction by reducing cross sectional area and the water shoots out much faster. I think the trick with head flow is to find the proper ballance of the 2 for your particular engine combo.
