16 years ago when I fabricated a cab on my little tractor, I paneled it with 1/8 plexiglass in thin plywood frames, screwed to the angle iron frame of the cab. I would take the door and three major panels off in the spring and replace them before winter. Over the last decade and a half, some of the plexiglass has cracked and the plywood has degraded, so this fall I decided to replace most of the panels with lexan. I modified the mounting system from through bolts to brackets, then used the old plywood frames as templates to cut the lexan to size. Here are the first pieces test fitted to the right side.
The lexan is 3/8 of an inch thick. My local autoglass place had a sheet in stock for a year and gave me a deal on it. A lot heavier than I felt I needed, but I doubt any tree branches are coming through this stuff.