If it is anything like the Model S, I'm guessing if you sit inside the car while someone takes the side of their closed fist and hits the hatch glass you will clearly hear the Boom, Boom, Boom. I did a bunch of deadening in my S hatch area, but it was only the firm rubber stoppers (cut down from solid rubber dowel) I made that ever made a material difference - similar to what you guys discovered with the PVC stoppers some of you are using. I did, for the record, try PVC back in the day too, but found the solid surface transmitted higher pitched vibration (note: I replaced all the rubber with pvc when I tried that so it acted too much like a solid bushing.).
Oddly enough, I stumbled upon the hatch movement thing when I test drove the car with blue painters tape stretched tightly 360 degrees around the hatch gap. At that time, I thought there might have been some Hemholz <sp> effect going on with air leaking past the gasket. Only later did I realize that tape was just holding the dang hatch more firmly in place. I know it seems like "tape" wouldn't be strong enough to do it, but it has some pretty strong tension when you put enough on there. p.s. I did the test drives at night....sort of embarrassing driving around with tape all over your car.