Wanted to follow up to see if someone can help. Looked at the glass in more detail this weekend. All glass on the model 3, to put it in layman's terms, is a "sandwich". Looked at my Volt and the front glass is a sandwich but the rear is one thick solid piece.
I push on every outer edge and the glass does not move on the Volt. On the Model 3 it's a different story. Near the trunk there's no flexing but all three pieces at the top flex and the windshield is the worst. I'm guessing it moves about 1/8"-1/4" at the edges of the top when I push it with my finger. That seems odd.
But getting back to my cracked rear glass. I took a ty-wrap (plastic) and could get it in about 1/8" (between the two pieces of glass) in the area around the crack and just about the full length of the trunk. Also, the top glass overlaps the bottom glass where the rear window meets the trunk. In other words, they're not lined up top to bottom. That means that if something strikes that area, it can easily break as opposed to if the two pieces of glass overlapped perfectly and the black stuff inside went all the way to the edge. I checked the sides and top and those area seemed to be better. Meaning, they don't overlap and the black stuff is right to the edge.
As stated before, the Volt glass is rock solid and has no gaps or overlaps. Don't know much about glass but wanted to know if anyone can shed some light on this problem or look at their Model 3 to see if these issues exist on their cars. Between the flexing glass on the roof and the damaged glass in the rear, I don't get the warm and fuzzy feeling from this car that I should be feeling.