Hey guys. Dark_Shadow- good idea. I did check that. That drove me nuts on a 4Runner I once owned and it turned out to be that. Crazy.
Here are the photos. This is the right rear of the roof as you can tell, and the piece that I cut is about 12" long. The key, I've found, is getting it between the frame edge of the sunshade and the roof of the truck. You'll notice a little bend at the back and that seems key. I do not know how far forward this needs to be - probably not much if the noise is right at the back edge where the shade frame starts. I'll start cutting this back a bit to see.
Let me know if you have any questions, or if this works for you.