Offtopic: Helmet to helmet contact

But if you spear someone, which is clearly leading with your head, you have your arms out. Clarks arms were tucked. The helmet to helmet contact (which I do not deny) is caused by McGahee's helmet coming down, now by Clark's helmet coming up.

I'm just gonna go ahead and say it. BS. If anything, I'd say it's opposite of what you're trying to say. It would make more sense for a normal tackler to have his arms out, so that he can wrap up after the impact. I know that's how I was taught.

You can spear, with or without your arms spread. HOWEVER, if a player is really thinking about spearing, or h2h contact, it would be in his best interest to make himself as compact as possible. That holds true for pretty much all tackling and impact, but truer when a player is relying on a single, blunt-force hit, like one delivered by a spearing motion.