I have never been on the ferry actually. Always drove everywhere. I was supposed to be coming to the lake in December but I don't think it will happen now
so, the roof box dimensions are 140*80*44 (here the description, I bought it over ebay for 90€!)
roof bars are from an italian brand LaPrealpina, bought both bars and 4 antitheft locks! (bars and locks!)
now with the winter season and low temperatures I'm experiencing the utility of the roof: opening it at the 1st fold will change air, give you light and not affecting inner temperature at all! no wind and no messy air or stiffneck