RE: Who said that physics wasn't fun?
Dude, you missed the point. Your arrow's that always result in pass through do so not because of the KE of the projectile presented to the target, but because of the momentum of the projectile presented to the target. I hear KE referred to as doing all the work of the arrow. That is simply not true. It (KE) is groovy stuff to be sure. However, it is not the whole picture. Besides that, I not sure where you find people that are "all caught up in the mass thing", as I almost never hear about mass. I do, on the other hand, hear about KE/speed ALL THE TIME!