A few follow-up points:
I found a video of Doug Weldon's presentation on the windshield damage at the 1999 JFK Lancer conference. In the presentation, Weldon spends some time talking about the damage visible in Altgens 6 while showing an enlargement of Altgens 6 on the jumbo screen (which appears to be about 6 feet tall and 10 feet wide). The segment starts at 1:40:34 in the video.
Doug Weldon JFK Assassination Conference Presentation: Kennedy LimousineI'm citing Weldon's presentation in part to show that we've known for many years that windshield damage is visible in Altgens 6.
Part of the evidence of a hole through the windshield is the fact that Kennedy had two small holes in his right cheek. Tom Robinson, one of the morticians, noticed the holes and plugged them to keep them from leaking embalming fluid. He didn't notice the holes until he started the embalming process and saw embalming fluid leak through them and saw a slight discoloration them begin to appear in them.
A number of scholars have suggested that small particles from the windshield shot hit Kennedy's right cheek, and that a larger glass fragment hit him in the throat. The glass fragment would have been hard to see on the chest x-rays and could have easily been missed. Also, the glass fragment's range would have been limited, which could explain the damage to the right lung slightly below and to the right of the throat wound.
BTW, Robinson told the HSCA that he saw a small wound in the area of JFK's right temple. No wonder his HSCA testimony was sealed. (It was released by the ARRB in the 1990s.)