Calling Mr Budster..
Aha!
Our solution over the last 12 years has been a rubber backed waterproof picnic rug.
Wrap the case in the picnic rug. Secure with gaffer tape, in the style of a wrapping a Christmas present.
Secure on the luggage rack with webbing straps.
Once at the hotel and off the car, the picnic rug can then be used for its intended purpose.
