We took off the gerbil couch cover. Then we removed the seat cushions. The seat area had minimal support. I cut a 2x4 piece of lumber. Tried to brace it across the couch for support. Had a rough time getting in in past the arm rests.
After that, we had a single 2x4 lumber diagonally on the seat area. I got smaller length 2x4 lumber to brace the other areas. Momoko said there was support, but she felt like the seat was leaning her forward. I added a 1x4 board across on the front of the couch. For now the thing is working.
Eventually we will need a new couch. Maybe then I can pay somebody to deliver and remove the old one.