Are you using the glass as a bezel as well? Depending on the type of bezel you decide to use, or if you care about this being seen, you can make a kind of frame inside of the cab around the edges of the screen area, so the glass can rest against that (I assume it’s going to be at some kind of angle..), then, in front of the glass you can put some small strips of wood screwed into the sides/top (probably only need to get two corners, top right, bottom left, something like that. And they should hold it down. You can paint them black, and they should hardly be noticeable.