First, was the target these marksmen were shooting at moving at the same speed and at the same distance and angle as JFK's motorcade? Yes, a concious effort was made to objectively simulate the same conditions, albeit without a sitting President riding in an open limo.

Second, were these marksmen considered comparable or better shots than Oswald? I believe that LHO had 2-3 different shooting scores (sharp shooter / marksman) while serving in the marines. CBS tried to find similiarly graded shooters. I think the old CBS show is still on you tube somewhere. I will see if I can find it.

Third, one has to take into account the extreme nervousness that would be present in the shooter at the moment he's taking aim at the president. I'm not sure they can really recreate that. I agree. There is no way to simulate that. There have been multiple efforts to sort out the number of shots and the timing of the shots that killed JFK. I am satisfied with the available evidence that it is possible for them to come form one gun and one shooter. But that is my opinion, and others are certainly welcome to accept or believe what they wish.