So you wanna rely on what they label a "conscious reaction" vs a "startle reaction"? I would contend the seven witnesses have been "noise conditioned" by the consistent backfires of the DPD motorcycles which are spread throughout the motorcade. That "reaction" well was poisoned by all of the motorcycle backfires.
Since all seven of those witnesses were, according to you, already conditioned to hearing shot-like sounds (does a motorcycle backfire produce a supersonic "crack"?) that day, their conscious (i.e., non-"startle") physical reactions -- as "captured" by the Zapruder film -- to the 1) muzzle blast, and 2) the supersonic "crack" of Oswald's first, missing-everything, shot must have been slower than if they weren't "conditioned." And therefore it must have occurred even earlier than "Z-124".
