RE: Arrow penetration vs. weight
Let's see if I've got this straight. You're taking two 2216 arrows of different weights, which means that they would have to have different lengths and/or tip weights to attain the weight difference. In any event they could well have different spines. You're comparing them to an unknown length, unknown spine and unknowndiameter Beman carbon arrow (unknown at least to us).
We also weren't told as to whether or not they were even shot out of the same bow and if that bow was properly tuned to any one of those arrows. And as stated, the medium into which the arrows were shot even complicated the puzzle. A better test would have been to build a set of identical arrows and increase the weight of one in a variety of ways.