I've got many. Here's my topbox mount and rack.
Having an Adventurer I don't have the 2 piece seat and wanting to have the topbox over the rear seat I had to do it another way. The rack is attached to the stock GSA rack. The mount straddles the rear of the seat also attaching to the stock GSA rack on each side.
For a rock solid mount and eliminate flex I added a .090 thick doubler with bends that match the bottom of the topbox.