It bugged the crap outta me. Not wanting to get involved with taking the shell off and removing the cab ( if possible) and /or figures.
I took some clear plastic from a Miller sign package( suggested by gunrunnerjohn on another thread) and cut pieces a bit wider than the window frame and about as tall as the cab so it would stand up on its own.
I slipped them in through the back of the cab and positioned them upright with some Q Tips. With the windows leaning back against the firebox I bent some stiff small guage wire so I could put a drop of canopy adhesive around the inside of the window frame. Then I pushed the window up against the frame and adhesive with one Q tip from the rear of the cab and one through the small front window opening and help there a couple of minutes to set.
Now I can sleep a little better tonite, and it matches the catalog description .