I have a Givi topbox. You don't take the original rack off; the Givi plate fixes above it (leastways, I don't remember taking anything off and can't find any spare bits of kit in the garage that seem to have no purpose.). If the Givi side rails use the holes in the frame that Yamaha left for their own panniers, you have to take the rear light off to get access for the rear fixing nuts. If they'd only threaded the holes it would have been oh so simple (You didn't tell me that Dave!)