i have a trio of 44ltr kappa cases on my triumph, on givi racks. they have proved to be completely waterproof, tough and good value. gives me an enormous capacity, i usually keep the topbox empty for my helmet, gloves and jacket when i stop.
i got them cheap on ebay and i noticed someone doing full sets of kappa or givi cases including racks for £240.
the only problem i have found is the keys are made of cheese! small brass keys in brittle plastic handles that shatter very easily. my cases are "keyed alike" (identical locks and keys) so i had 9 identical keys, now im down to 2! get some metal keys cut asap