I put on four. I used .125 thick aluminum about 2" x 3". I padded them with thin cork and bent them to match the contour to avoid cracking the glass.
But to get real... On later cars and trucks, the front and back glass is glued to the body with high strength silicone glue. It will not "push" out, it shatters. You have to cut the glue to get the glass out.