couldn't hurt. I like your idea in the picture, but I think you'd be better off if you could get it to come all the way to the cab - probably lots of air running right against the window that you could smoothen out, plus if you don't get all the way against it, your air deflector could act as a parachute and hurt drag, or worse, rip off!
Welcome to ecomodder!
Any other mods planned?