If I were you, I would purchase the Garmin Professional Vehicle Mount which allows you to mount the Sat Nav unit on the vent of your air-conditioning or by your centre console....if not I believe they do sell grey units which can hold to ur Nuvi series. Well, that's what I'm doing to my 310 atm so it's not visible from the outside.
Drawback : You really have to sit down and mount it properly as mount it too far, you might not see it but mount it too near and you might get distracted by it.
Drawback : You really have to sit down and mount it properly as mount it too far, you might not see it but mount it too near and you might get distracted by it.