Having some experience with enforcement and glass legalities in the offroad communities I can tell you that all they care about legally is the front glass.
All the other windows don't have to be there at all to be legal.
Actually if you wear eye protection you don't even have to have the front glass to be legal.
Notice those side by side ATV's running around on the street?
NONE of them have glass, and the ones that don't have a windscreen at all have goggles on.
That makes them legal.