I had given up hope on the rattles. Every fix attempted only made them worse.
Then the right master mechanic happened to pull my car around to the service bay. He heard the rattles right away ... and fixed them! There is nothing like driving down the road, even hitting seams and bumps, and having no rattles! It's a new car! (Well, it really is pretty new, but the rattles were there from day one. Not any more!)
Don't give up hope. Find the right fix.