This is simply and only my two cents. It won't change the debate one iota. But...
I am a shooter and I am at home when at the range. I have hunted deer since I was 12 years old. I load my own ammunition. From that experience, I feel I know how to shoot. I have never been in the military.
I have been in the book depository perhaps a half dozen times. I have been on street level in Dallas more frequently than that. The shots taken by Oswald were not difficult. The motorcade was moving away at something like 20 mph and nearly in the direction of Oswald's line of sight giving the target a near stationary attitude. I have seen and made far more difficult shots with successful follow-up shots - many times.
Also, keep in mind, a fired bullet in flight is a projectile heavily loaded with energy that relies on a gyroscopic spin to keep it stable during flight. But, once it strikes something, it can take very bizarre and erratic paths.
So... it is my belief that Oswald was the lone gunman that day. President Kennedy's death was the result of a tragic nexus of a crazy gunman and opportunity.