I don't know if the above will help you out or not, but we, as can be read in the above post, are trying to add some "home made window protectors" ourselves. If you click on the pic, it will give you the chance to enlarge enough to see the snaps at each corner. So, at least, by getting the measurements of the snaps, it will give idea of adding rivets and not hurting glass, I think.
Leigh (IB Aluminated)
"When a great ship is in harbour and moored, it is safe, there can be no doubt. But that is not what great ships are built for." by Clarissa Pinkola-Estes, author of ‘Women Who Run With the Wolves’