I think one of the biggest down sides to buying a pre-owned RV is dealing with the previous owners choices. The previous owners of our camper made some...um, unusual choices. One of those choices was to remove the seat back from one side of the dinette. Consequently, every time we leaned back against the dinette cushion we would fall back or the cushions would get jumbled. So, it was time to replace the seat back they had removed. We came up with our measurements based on the height of the back cushion and length for weight distribution. Using a quality piece of 3/4" thick MDF we cut the board to length and rounded the corners with a hand sander. The board was smooth but we did do some touch up sanding to give it a nice even feel.
After sanding, the board was spray painted the same espresso color as the rest of the cabinets.
Once everything was dry it was time to install. We purchased new silver hinges from Home Depot making sure that the new seat back could lay flat for transportation.