Creative Speculation

"That is not the 2.5" head-snap; Fiester does not address that at all, apparently because she is unaware of it…"

Chapter Seven of Fiester's book, which runs over 30 pages, is entirely about the forward head snap. After noting that "Rifle bullets carry between 1100 to 3300 foot pounds of force;…" Fiester demonstrates -

"The higher a projectile’s velocity upon impact, the more kinetic energy is available to transfer to the target. The amount of kinetic energy transferred to a target increases with faster projectile deceleration. This initial transfer of energy causes the target to swell or move minutely into the force and against the line of fire. The greater the transferred energy, the more pronounced the forward movement (Karger, 2008; Coupland, 2011; Radford, 2009)."

Let's repeat: The greater the transferred energy, the more pronounced the forward movement . Fiester refers to recent experiments (Ervin, 2011), whereby a gelatine block had a "forward snap" of 2 inches , which you insist cannot happen.

"Current forensic research indicates the forward movement of Kennedy’s head follow by a rearward movement is consistent with a single gunshot to the head from the front. Research by Karger (2008), Radford, (2009) and Coupland (2011) prove initial transfer of energy causes the target to swell or move minutely into the force and against the line of fire." ( Fiester p 264)

These peer-reviewed observations by actual forensic ballistic specialists are supported by the back-spatter pattern observed in the Zapruder film. Your position is informed solely by a paper written by atmospheric physicist which does not address any of the above information.