Found a 3D model with somewhat-comparable seated posture. The model has no articulation; the model is as originally-scanned. Back-projecting 17° upwards from Kennedy's throat wound as photographed at Bethesda leads to a "back wound" below any clothing bunch.
The base-of-the-back-of-the-neck wound on the model is about 3" below the top of the blue sweater. The orange outline from the Jeffries film shows the top of Kennedy's clothing at the nape is a little higher than that of the model, so this fits in with JFK's wound being 3½" below the top of his jacket collar (
Link ). That leaves two-inches of material to be taken up by a one-inch-high clothing bunch. That's how the bullet holes in Kennedy's clothing (as measured when hung straight on a hanger or spread out evenly on a table) was about 5½" below the top of the clothing.
Such a bunch is clearly seen in pictures taken throughout the motorcade. At least those pictures of sufficient resolution, camera angle and with Kennedy having his right arm over the car rail. The color picture above was taken as the limousine turned from Houston Street onto Elm, about seven seconds before Z223. The Zapruder film shows Kennedy had his right arm over the car rail all during the sequence before the limousine when behind the sign.
