has anyone attempted to make their own sofa?

I was thinking of doing the same thing. Remove Jack knife, add 2x2 framing. My water tank is under the trailer floor, so it will still be all storage. Will be putting removable plywood like the dinette seats and a strip of plywood secured at the back of the bench portion all the way to the wall for a base for the back which will also include special storage. It will have a flip down plywood panel and hidden latched for rifle, shotgun and ammo storage. Maybe some shelves for small items or extra canned goods or other food items. Was thinking about adding a futon mattress for the cushions (you can custom order them to the size you need) or get an upholstery shop make some cushions.

I did draw up a plan for a fold out sofa for a mini camper I am going to build using an enclosed utility trailer I have not yet purchased. It will use a twin size futon mattress. Daytime & evening sofa / night time fold out bed.