It is more about the build really. Also the build quality of the car/truck itself. Some do not get much flex ever some flap around when you just look at them.
i love when people come on here posting their ultimate goals in car audio.
like, can 2 8" boss audio subs on a 4000 watt boss audio amp pull a hair trick? because i saw Steve Meade on you tube and now i want to do a hair trick, hes my idol.
it all depends on vechale those year tahoes windsheilds are pretty straightup i dont think you will ever get any flex, hummers dont flex windshields and even look at steve meade tahoe and the smd escalade those windsheilds are semi straight and will not flex