I'm not sure I see the connection between size and likelihood of tearing an ACL. I agree about McGuffie, he probably wasn't physically prepared for Big 10 football and he got knocked around and suffered multiple concussions. His size, or lack thereof, was probably a significant factor.
V Smith's injury, a torn ACL, has absolutely nothing to do with his size. Even if there is some correlation between lack of size and certain types of injuries, it wouldn't apply to a torn ACL, IME.