I mounted mine to the stock rack, but ended up having to drill a couple holes in the new mounting plate of the rack to do it.
I took the stock rack off and drilled through the rubber pad in three places. Then I ran bolts through those holes and into the rack that comes with this case.
I then drilled holes in the new rack to access the stock mounting bolts for the stock rack.
First I attached the racks together and then used the four stock bolts to re-mount the racks onto the bike.
2007 Suzuki V-Strom 650