Has anyone considered a fantastic fan and a ceiling vent as well? This compact van has a ceiling that does not allow the space for a fantastic fan expect toward the front- right behind the driver's seat. I need something toward the back. This is a very small van but I need ventilation and would rather use the roof vent then crack a window any day. In hot weather or when I'm boiling water, etc I would really like the fantastic fan but I want a small vent toward the back too. Would having 2 openings cause additional problems or create any issues?