Stinger owners are not alone, have a quick look at Skoda Superb owners with similar irritating noises, on the Briskoda dot net site. Sorry there's no link, this is my first post, no links allowed
I've noticed that many vehicles with a large rear hatch/door/gate are much more prone to rattles, noises and squeaks than Sedans or Coupes
It is probably related to the long open floor loading area, and the subsequent lack of hard metal support (or bracing) across the vehicle between the two rear suspension mounts.
In Sedans or Coupes there is invariably a large solid braced sheet metal rear
seat attachment, as well as a fairly solid rear metal parcel shelf.
A massive hinged rear opening and closing hatch (mostly glass) is not going to do a lot for rear structural rigidity !