Bought a used coach that came without the sofa. We have the two of us and our son using the motorhome just about every weekend of the summer. We have 72" of width available in the slide for the sofa...
How about a futon: it can be put together in place, and the mattress is more comfortable than a folding bed. I mention it because we just vacationed with kids and grandkids. The adults put a futon cushion on the coach to make it more comfortable. We then carried the pad to the back bed in the daytime to keep it out of the way. Just an idea.