He's trying to add a second bullet to the head, and he's trying to make the primary shot come from somewhere else other than the TSBD.
To do so he is ignoring the known visual evidence of the two films of the assassination, and he ignores a huge chunk of basic reality to reach for his fantasy. He ignores the fact that the President's head was not level with the shoulders, that Elm Street is inclined, and that it was a short-range shot.
Like all CTists, he places an unrealistic level of expertise upon the Secret Service, FBI, and the Warren Commission that we don't even see today with all of our high technologies. Like all CTists he assumes all human recollection is 100% accurate, and does not degrade with time...unless someone witnessed something which undermines his theory, and in those MANY cases those witnesses cannot be trusted.
I used to play the same game.
I wanted Badge Man to be real, I wanted there to be someone else on the 6th floor with a Mauser, I wanted a direct chain linking Oswald to Ruby to the Mob to the CIA to LBJ to Hunt Oil to the military industrial complex to...THEM! I read every JFK conspiracy book, Mark Lane and Jim Mars were my prophets. People who bought the official WC conclusions were suckers, sheep, or blind, and I was smarter than all of them because I knew the truth....
The "Truth" is that eventually reality will kick you in the groin, or somewhere else where you can no longer honestly believe silly things and look yourself in the mirror, and believe you're a moderately smart person.