Re: custom folding rear seats bowrider?
Are both top and bottom cushions removeable? If so, you can mount a folding seat to a piece of plywood that matches the dimensions of the bottom seat cushion board, and add back in any locating piece of wood.
I used some plastic decking "wood" when I did this for my boat. Worked pretty well. The old cushions were rotting away and I really wanted some better looking jump seats back there. The original old square cushions on mine were designed to remove and mount higher to fill in from side to side and make a sun pad but I was not interested in keeping that functionality. The available aftermarket jump seats with boxes would make it hard to access the battery and bilge pump , etc. I wanted to keep the configuration from the original so that was my solution. I got some good looking comfortable seats for the price of one boxed jump seat and can still reach under them or even take them out for full access.
I do not have any pics, sorry. I will be working on the boat this weekend I hope and can post pics if anyone is interested.