I would bet anything that the arrow you got that weighed out the same as a 2315 is NOT 100% carbon. It's one of the carbon/glass composite arrows. Carbon Express Terminator, if I was to make a semi-educated wild@$$ guess.

The weight is one of the things I like about them, but that's beside the point.

Overdraws are pretty darn obsolete these days. Brace heights are too low to use a meaningful overdraw. You set a 5" overdraw on a bow with a 7" brace height, and you're gonna tear something up. Besides, you can set most standard rests back enough to get the equivilant of a 2" overdraw.