I would reckon wind deflectors would work, they actually dont attach to the window, its the inside lip of the window sil if you know what i mean. Think of it, you can open your window fully and the wind deflector is still there.
Yeah good point, I'm sat at work thinking about it lol, to be fair there isn't much point in a wind defector if you have lexan windows anyway but just don't want to remove them Cheers lads