I believe weight/momentum has the most effect in penetration when it comes to
penetrating through animals. Shaft diameter to me is less of an issue unless you
are shooting into stacked cardboard or simular materials. The smaller diameter
shaft will almost always out penetrate larger diameter shafts with fieldpoints in
this type of target, much less resistance. In hunting situations, the shaft will follow
the path the broadhead has cut through the animal no matter what it's diameter
is. (i.e.-aluminum shafts). So to me shaft size is less of an issue when it comes to
penetrating through flesh. A straight flying arrow, a razor sharp broadhead, and
the momentum to go through the animal is what is important to me.