The border is only a 15min drive, so it's close

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If I can leave it at home I will 'cause I really don't like how it affects the handling + the added height. Some "télépéage" booths have a 2m height restriction, almost forgot that a VW Caddy + roof box is roughly 2,4m high could have gone bad.
But on skiing trips it's either the roof box or two cars since we take our own skis with us and my wife hates driving for longer than 1 hour. Or when we take the dogs with us there isn't enough room left for luggage either.
On the other hand I was far from the only one with a roof box making the trip to or from the alps.