Just remembered looking at motorbike paniers clipped to lockable mounts on the rack.
Givi is a good make.
Not cheap though
That is the approach I use. Comments above re the cases sitting high are true. This year, I plan to adapt a John Worrall Low Line Luggage Rack. This way, I can make the pannnier bracket mounting more secure and also swap back to the rack with side screen stowage when not on a long touring holiday.
