The first thing I needed to figure out was how I wanted to attach the benches to the boat. There are brackets riveted into the hull of the boat, but it seemed like sliding a carpeted piece of plywood into that bracket would be a pain in the neck. (The first picture below is of the bracket.) I also didn't want to carpet over the metal bracket itself like the previous owner did.
I decided the new benches would sit on top of the bracket. The problem here is that the new benches are then raised up higher than where the original benches were. This means then are too high to get any support from the aluminum sides of the bench that hold the foam.
What I decided to do was cut a plywood "skeleton" to slide in to where the old benches were. I cut a lot of wood out of a few of these skeletons, but they still provide support and allow the actual benches to make contact with all the support the boat provides. It's a little bit of added weight, but it's not much.
There are a lot of pictures below.