BBold,
Drewsbow is right on, spot on. I have found the same thing when dealing with carbons at the lower draw weights.
I shoot carbon, in fact my girlfriend shots grizzly sticks at 40-45pounds. I still believe that aluminum is the way to go. They are uniformed in weight and spine, and they have a lot of different sizes that don't force a person to take marginal spine.
There is no doubt that a carbon arrow will get more out of your bow, but you can get good weight out of aluminum too. I have even added weight to the insert to get the FOC correct.
That is why my lighter weight bows always eat aluminum.