Mike,
Ours have a cover on them but it is not removable.
Are you happy with the mattress supplied? We just spent three weeks on the road and we both found the mattress a bit thin. My hips were starting to get sore by the time we got home. I'm investing a replacement mattress but have not made a decision yet.
Yes, ours has the sew on cover but that will get dirty over time so I know we'll need a slip on cover of some kind.
Mattresses: Ours are interesting as the passenger side is noticeably harder than the driver's side. I have liked the soft driver's side (my chosen side) but it is already beginning to form a body shaped sag in the middle. (no weight comments please!

) My wife's bed has retained its shape but she finds it too hard so we have just added a mattress pad to see if that helps enough.
I wondered from day one how two mattresses could be so different from the same company.
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We haven't placed the cushions on the back of the bed, couch-like, as we often will stretch out on the bed to read during the day and that makes the bed too narrow.