We use two foam toppers. We used to use them in our Roadtrek, one each on the 'twin' beds. They're now approx 25" x 70" (used to be 27") and might be 3" or 4" foam. I fold them in half for storing in our Trail-lite. One goes behind the drivers seat and the other goes behind the passenger seat. They have a fleece covering. I trimmed them down to 25" to make it easier pass by them coming from the cab.
We used sleeping bags in the RT and continue to use them in our B+.
I've been wondering if I'd be able to store two rolled up pieces of memory foam in the space now taken up by the large Television.
The sofa and dinette seem to be the same level when made up as one large bed in our 213. No gaps that I can recall.