Show us where he said there were only two shots. He always said he heard only two shots. He has said many times that he accepts that there were three shots. He has always maintained that JFK reacted to the first shot by hunching forward and to the left.
Re: standing on running board at z306. We do not have a visual record of when Hill stepped off the running board. We know it was after Altgens 6 at z254-255. It is difficult to estimate how long it took for him to get along-side the front of the QM when we first see him in the Nix film. He does not reach the rear hand-hold until z338 which is 4.5 seconds after Altgens 6.
I expect that when he stepped off the running board and hit the road, he was not immediately running at the car speed and probably went back a few feet before running faster than the car. If he left the car at z265 that would give him 4 seconds to make it to the back of the limo at z338.
If he leaped off at z307 that would give him 1.69 seconds to get up to speed and dash the 14 feet from the running board to grab the handhold:

That is not much time. He would need to average 20 feet/second or 14 mph from the time he jumped off the running board until reaching the hand-hold (assuming the limo was moving at 12 feet/sec or 8 mph).
I would suggest that 4 seconds is probably closer to the actual running time.
Clint Hill stated there were only two shots.
Mr. SPECTER. How many shots have you described that you heard?
Mr. HILL. Two.
Mr. SPECTER. Did you hear any more than two shots?
Mr. HILL. No, sir. You actually believe in the 1/3 of a second between Hill jumping off of the running board and the headshot, that there was another shot he did not hear? Really?
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I would suggest that 4 seconds is probably closer to the actual running time. Only because you made the whole thing up and really have no idea what you are really stating.
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Clint Hill jumps off the running board at Z307 and grabs a hold of the handholds on the back of the limousine at Z337. The speed of the camera is 18.3 frames/second. That is 30 frames. 1 Frame is approximately 1 foot of car travel. It took Clint Hill 1.65 seconds to reach the handholds. He ran at a speed of 30 feet per 1.6 seconds or 18.75 feet per second.
18,75 feet/second is equal to 12.8 mph.
(18.3 frames/sec x 1 foot per frame is 18.75 feet per second. Divided by 5280 feet per mile equals .003 miles per second X 60 seconds per minute x 60 minutes per hour.) ---- 12.8mph
12.8mph is very doable even by your standards. Average sprinting speed of a male is 14.5 mph or 21 feet/sec.
A Mason: 12.3 mph estimation. 72 feet in 4 seconds. Z265 to Z337. Taken from completely made up crap from an overactive imagination.
Muchmore film actual calculation of Hill's movements: 12.8mph. As viewed for real in the film
What is your problem again?
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SA Kinney, driving the SS car, states SA Clint Hill never left the SS car until the headshot. But do not let that fact get in the way of this weird theory.
SA Kinney also had the second shot as the headshot. The same as Hickey. Hair flying: Kinney and Hickey were roommates and both reference the hair flying.
But do not let that get in the way of this useless nonsense you are promoting.
SA Kinney 11/22/63
Index Frame (history-matters.com)
I was driving SS 679-X, follow-up. As we turned off Main Street (left) about 4 minutes from our destination of Trade Mart.
The first shot was fired as we were going into an underpass. The first shot was fired, I glanced from the taillight of SS 100-X, at the President and it appeared that he had been shot because he slumped to the left. Immediately he sat up again.* At this time the second shot was fired and I observed hair flying from the right side of his head. With this, simultaneously with the President's car, we stepped on the gas. I released the siren at that time. I did hear three shots but do not recall which shots were those that hit the President.
*At this time Clint Hill jumped off and ran to the President's car, jumped on the back, and laid out across the trunk in a prone position where he rode the entire trip to the hospital.