I am not a rifle shooter so I have no expertise at all on which I can draw on from my own experience.
However, I find it strange someone can dismiss the comments of such people as Craig Roberts, Carlos Hathcock and Hubert Hammerer but then rely on people that have never used THE rifle from the 6th floor window against a similarly moving target with the tree in the middle of the shots.
Could Lee Harvey Oswald have made the shots? Possibly he could but why not make sure and shoot him as he came down Houston in a straight line and getting bigger ever second? Why not shoot when the limo was going barely a few miles per hour right beneath the window, hell he could have thrown the rifle at him.
When someone uses CE139, from the 6th floor window and replicates the shots attributed to Oswald THEN and only then can we say it was possible. It would also need to be done by someone that was the same ability at shooting that Oswald was. Or do you think the 3 Master riflemen that were used to test the rifle that fired from only half the height at stationary targets is a fair recreation of the scenario then you might as well say that Oswald could run 100m in 10 seconds because Usain Bolt can
The comments (professional opinions) of expert marksman are worth consideration if they have gone to the crime scene. If your boys (Roberts, Hathcock and Hammerer) have not traveled to Dallas and looked out the 6th floor window of the TSBD from where the shots were fired, their estimates are of little value.
Would their opinions be based on descriptions of the shooting by the:
-- Warren Commission?
-- House Select Committee on Assassinations?
-- the writers of various books and articles?
-- assessments or reconstructions in Television documentaries?
Probably some or all.
Your speculation as to what's better in terms of direction and trajectory are "either/or propositions". Do you comprehend: The assassin might choose the poorer of two potential shooting methods and yet still be successful.
All assertions about "the best or better way" shooting sequences are subjective... and they do not consider the "wrong way still worked" possibility.
My "boy", the late Howard Donahue participated in the 1967 CBS tests and made the shots. It was not a perfect reconstruction but similar enough to prove that the shots attributed to Oswald were possible.
We are way off-topic... but hey it's my Subject and I'm obliged to answer all comments or I'll be branded a "dodger".