So you'd recommend moving up to 100 grain heads and the 10.2% FOC? All this is science of arrows is relatively new to me as I had never given it much thought. I couldn't tell you if I'm getting good broadhead flight since I haven't shot them yet - field points only.
...and I think that is going to be the critical test. If you get good, consistant groups with broadheads then I, too, would not worry about the FOC. However, if you do see poor or inconsistant groupings with broadheads then you may want to experiment with th 100 grain Muzzys.