As anyone who rides two up with the factory topbox setup knows the position of the topbox is way too forward and really makes it a tight fit between you and your passenger. I looked for a solution online and didnt find anything you could buy to move the box back with the standard rack. I had a piece of 1/4 x 1 3/4 steel barstock that was welded to 10 1/2 by 12 1/2 laying around in my garage (maybe from a bike stand I think) but it was the perfect size to use as a repositioning mount for my topbox. I drilled a few holes and installed the stock pins for the box to slide onto and two more for the locking mechanism and besides painting that was about it. This moved the box back 3" and really made a huge improvement with a passenger aboard and is very solid.