Instead of relying on your biased interpretation of what you side believes Hill was saying let's let Hill show us what he meant and what do you know here we see Hill describing precisely what is seen in the Zapruder/Autopsy photos/X Rays.
Here's where we insert a quote of Mytton or one of his buddies explaining how decades later recollections are inferior to earlier accounts.
It only happened one way:
Mr. HILL. The right rear portion of his head was missing. It was lying in the rear seat of the car. His brain was exposed. There was blood and bits of brain all over the entire rear portion of the car. Mrs. Kennedy was completely covered with blood. There was so much blood you could not tell if there had been any other wound or not, except for the one large gaping wound in the right rear portion of the head.