It is mostly a matter of finding one that fits, There is quite a bit of variation in distance from back of sofa to head of mattress when open, some sofas made for RVs take up less room than many residential sleepers. All will come much further into to room than a jack knife, will use some or all of the aisle. Some may not fit opened, you'll need to measure the pace you have in the RV before you shop for the sofa.
Some of the RV sofa beds I've seen have ben shorter than a queen, to make more room at the foot of the bed, or to just fit the space available. Most I've seen in motorhomes have been powered, needing a power source.
Other consideration when shopping for the RV, what use was made of space under the Jack knife. If just storage accessible from inside, usually OK. But if space was used for an external storage bin, a water tank, furnace, electrical equipment, replacing the jack knife with something else means relocating these other things.
I think Phoenix Cruiser has at least one short C with a powered foldout sofa in a front slide, we looked at it at the 2004 Tampa show. Don't remember a dinette opposite, may have had a bench or chair, with a removable table for in front of sofa, remember wife asking about where table is stored, because earler that day a RVision rep couldn't answer that question about a small A we looked at. Coachhouse also uses this type of sofa bed. Neither brand will have the overhead bed for grandkids.
Thing about small Cs you might be missig, there is only so much room for what everybody wants, so you start making compromises like sleeping lengthwise on narrow beds, not having a dinette, smaller bathrooms and kitchens. A few feet can make a big difference on what can be done inside, little in handling or where you can fit it, 25 is a nice number, but a difficult compromise, because for parking, once past 19-21 feet, it might as well be 30.
