ORIGINAL: DARKWAV
When I cut out a clear body shell I save all the trimming. When you get a crack you use the Lexan trimming as backing and use the Shoe Goo adhesive so you end up with a very strong repair no matter how big the crack is. Since the trimmings have different shapes and profiles you can usually come up with a backing peice that has a profile or curves that matches the cracked part of the body close-enough. I also use trimmings to re-enforce the holes for the body posts.
Good idea -but most cracks can be eliminated by smoothing the edges (using sandpaper, or dremel) after cutting out the body so as to avoid any rough or snagged edges, along with avoiding any sharp cut corners (which was why the OP's body cracked at the windshield corners). Then reinforcing with ShoeGoo any hard mold edges, particularly where there's any 90-degree corners (a truck's doorpost meets the body), and especially the front fenderwells or any area that takes repeated flexing.