Was talking to someone the other day who has something similar on his Pan , his has a roof box from a car mounted on a chassis with a rack on the top for all his camping gear for a family of four for two weeks (his wife has a bike as well).
Apparently it is narrower than the bike with panniers on so filtering isn't a problem (max width allowed on a solo is 1 metre).
BUT you cannot use the outer lanes on autobahns and you are supposed to go no more than 60mph over here , same as a shed dragger!