From the chart you are well above the minimum recommended. I sounds like heavier arrows will drop your speed and not have as flat a trajectory, but might have more Kinetic energy for penetration. I am not sure if just a different broadhead would have the same result but keep the trajectory and speed of the lighter arrow.
http://bowsite.com/bowsite/features/...r/penetration/ For the KE calcs. I guess you need the speed of the arrow, so you can compare that way. You can play with the calculator deal on this link, but if the heavier arrow drops your speed you end up with the same or less kinetic energy, but not as flat a trajectory, so no advantage. I am not really sure, just some stuff to look at. The arrow construction and stuff are some other things to look at it sounds like. It could be a good debate.