I love the stern rail seats on my h260 but I find the factory seats a little uncomfortable. I decided to make some larger seats to make it more comfy for guests on the boat. I first made some out of plywood and tried them out. I adjusted them a few times and when I was finally happy with the shape I cut out a final shape. I used 3/4" UHMW for the material and used the rest seats as a template, rounder over the edges with my router (1/4" bit) and drilled pilot holes for the underside screw nails that fix the seat to the rails. Because the new style of the seat hangs out over the rail further than the original did, I was concerned that this would put too much additional stress on the seat attachment points. To strengthen that precieved weak point, I added additional screw nails along the rail by drilling pilot holes in the rail similar to the existing ones. I wanted cushions for the seats and more importantly I wanted some type of cushion for the top rail where your back rests. This I found greatly reduces the comfort of sitting up on the rail as your back cant get comfortable resting along a 1" metal rail. I tried a few ideas before I came across a replacement tractor seat and back rest from Pricess Auto. For my American friends, that is a store similar to your Harbor Freight. One set cost $12, so it cost me $24 for two sets. They come with a camouflage material covering them which doesn't work on a sail boat. More importantly if I left them as they were, most people would not see them on the seat being that they are camouflaged. So I ordered some Sunbrella material that matched my other canvas on the boat and made new covers. To attach the cushions to the UHMW seat, I simply added snaps. For the back rest I added four pieces of stretchy material with snaps that will hold it to the rail. Easy and quick to snap into place and to remove. They are very comfortable, a pretty cheap upgrade and are working great. the pic with the backrest shows the strapping material but no snaps. I have replaced the material and have not put the snaps on yet.
.
.