I can attest to the light weight of the squirrel not taking the full force theory.
I was a full blown runt in HS, weighed 65lbs my 9th grade year. I played football and wrestled all four years but until my senior year I never felt anyone hit me. I was so light they would hammer me and the only hit I felt was my head hitting the ground.
My senior year I was a huge 119lbs and could feel anyone under 200lbs hit me, but after that threshold I still hardly felt it till the thud on the ground. Kinda funny to get hit by the biggest guy on the team and not feel a thing.
The coaches thought I was nuts and tough as nails, little did they know I was so little I couldn't feel it!