I've noticed that it just seems that the right rear quarter panel just looks unfinished inside. The oppositie side is covered due to the fuel filler neck needing to be covered. Seems like it should have something similar on the right side.

 

I must agree. When I had my first FD there was a little rot back there and I thought for sure it was missing the plastic liner. I called Ray Crowe to get a replacement and he informed me there never was anything there.
I don't have that rust problem anymore (new FD) and I don't drive in the rain.

 

Yeah I have always thought the same thing, be a pioneer and make something and do a write up for us!

off topic but, S03's or RE05's? How do you like em?

 

Actually they are RE750's and I love 'em! Sticky, sticky tire with incredible dry AND wet performance. After having these, I can't imagine what the S03's or the new RE01Rs would do!

As for that opening....man, I would really like to come up with a functional cover of some sort that had a 'factory look' to it. Although the service tech at the local dealer (who amazingly is a knowledgeable guy!) was looking at it with me and said, "You know, Mazda didn't do ANYTHING on this car without a reason. I suspect it was intentionally left open to aid in cooling the exhaust."
I suppose he could be right.