I have to use a 3" thick foam mattress pad, which I got at Bed Bath & Beyond. I have had to cut it down to the size of my couch, because I don't open the couch into a sofabed. It's miserably uncomfortable with that dip down the middle. So I store the mattress pad behind the couch between the back of the couch and the outer wall of my mh. It looked like a mattress stuck back there. Really tacky. I found some dark grey chenille throws at Target that are a perfect size to cover and protect the couch upholstery and to cover the mattress pad. I bought one for the couch. I stitched the long edges together on a second one to make a sleeve for over the pad. Slide the pad behind the couch, and both match perfectly in a nice, small-ribbed dark grey. Really neatens the place up. I even got a third throw that I use as an actual throw, or as an occasonal nest for the cat on cool days. The stretchy chenille doesn't even move out of place when I sit or nap on it. And the cat's nails don't seem to snag it. Great stuff.
--pat