Taping Window on Cab Over

I wouldn’t have thought or worried about it, but I wouldn’t use cardboard. I’d be thinking like a piece of tub surround FRP or a piece of plexiglass. Cut to the shape of the window and stick on with some sticky back Velcro or maybe a few dabs or caulking or construction adhesive between the pieces or double sided tape for vehicle trim. I’d do Velcro. Easily removable later.
Doesn’t need to be attached terribly well just enough to not fall off from vibration and bouncing.