For those that might be interested, here is a simple and inexpensive fix for the oem top box rattle on the GT.
First, stuff some foam rubber between the bottom of the box and mounting bracket.
Then cut some one inch pieces of black electrical tape. Place tape on edge of box in the area where white lines are in picture. It may take 5-8 pieces per area. Add tape as needed to stop rattle.
This takes the slop out of the hinge pins.
I did this to mine and now it is quiet and shakes less.
Sorry for the funky picture.