2213, I have a question for you. You are asking some good questions here and seem to have a pretty good handle on things. But--- why do you want to compare the "light" carbon arrow and speed with the "heavy" aluminum aluminum arrow? It's pretty much accepted that carbon arrows, because of their smaller diameter, give better penetration. So, to get the best of both worlds why not consider a heavier, slower carbon arrow.
I've been shooting the light ones for years and am seriously considering going with a heavier carbon arrow myself. Not that I've had any problems with penetration. Just maybe beginning to think that I'll get a bit better penetration, more forgiveness, and a quieter bow. And basically, for normal distances within 30 yards, speed is really a non-issue, as is trajectory.
Just a thought, buddy.