On long holiday trips I've always used the very thick leather sidebags a friend had given me in 1980. They are of behind the iron curtain origin (like his Jawa was) and they have always served me well. The leather has become very hard now and they are far from waterproof. Even now I can still use them as I pack my gear in plastic (transparent) bags first. I avoid to ride in rain though: gentlemen don't ride in rain. The way I used to pack my iron horse resulted in a rock solid handling. The rack is a perfect fit. I dont know the brand but I remember it was marketed for CB500-550-750s back then. I believe it was German. You could also buy hard shell cases with them, but I did not. When my bike falls over - and this has happened quite some times - there's no damage, when a friends CB550 fell over his hardshell case leaked ever since. Also I remember a test in those days in a motor mag: none of the hard shell cases tested proved to be 100% waterproof. Also in countries like Greece and Turkey, they can repair a leather bag when needed just about anywhere. Hard shell cases can get damaged beyond repair. The advertised advantage of a click on - click off system, I find futile. I just open the lid of the leather bags and pull out the two or three plastic bags. No big deal. As for theft, I always parked my bike like near a terrace with lots of people. On all my trips, nothing got stolen ever.
