I usually only need a two-seater, like my dear departed 1982 RX-7, but the RX-8's back seats are nice for the occasions I need four seats to supplement the small trunk for cargo, shopping bags, etc.

I carry a light microfiber blanket in the seat bin, for warmth if stranded and to protect the back seats when carrying stuff.
Does anybody have a better solution?

How about foldup plastic or cardboard panels? Ideas?

I have a couple of thick towels in the trunk. They're not very pretty, but they're thick enough to protect the seats and the center backbone thing.