I did the shirt, I stuffed it with foam, the rattle always came back. The only solution is to remove the sliding door.
Its really easy and it looks fine you just have an open compartment in the back. All you have to do is just pull the compartment out, it's just snapped in. Once its out there are either 2 or 4 small torx screws, I can't remember exactly how many. Once you have removed them you can slide the door off the compartment. Put the screws back and snap it back in the seat and you're done.
I have exhaust and an intake...