Uh, yup. Chris has got it. The finned (slotted), black plastic plates or screens or whatchcallems, about 6" x 9", mounted in both the L and R sides, outboard of the spare tire well in the 700s, serve to keep whatever loose crap you may throw in there from blocking the flappy, floppy, flow-through vents that are outboard of them... on the outer body surface of the car.

Sure, remove them if you like, to gain an inch; that's about all. I did, when I placed the car's battery in the right side chamber back there, and ran cables forward to the engine bay. (Part of the battle against winter... childhood dream realized, doncha know: not to gain traction on some prissy dragstrip, but in the everyday circus that's Winter in the upper Midwest.)

How do they fasten? Jeez. It's been too long. But I know it was sinfully easy. Why not grab a flashlight, a 10 mm socket, and bend over and look?!
--
Gregg in MN