Back cushion support in the forward dining area,mods

I would help if you could post a picture of the area your dealing with. On our old hybrid one end of the dinette was the end wall of the trailer and the other was part of the dinette box.
In our current c-class, the dinette the area is a box with supporting end walls from the floor up. Actually the front, (behind the passenger seat) has a hinged cutout so that the passenger seat can recline.

Ken