Strange question - but has anyone fitted a roof box on the 380? Trying to work out what is a reasonable size.

The one I am looking at the moment is 480 litres but is quite long @ 1.98 metres?

Has anyone experience with these roof boxes to tell me if this length is too big for the car?

I measured it on the roof and it seems huge compared to the 380 roof line. But I have no idea about these boxes.