Here is a detail photo of my seat rail build. I used off the shelf seat rails for a riding lawn mower or skid steer. They are a little heavy, but work well and are very solid. I used off the shelf 3/4x3/4 aluminum L angle from the hardware store to build the supports. As you can see, the supports reach from the front of the seat pan to the rear cabin rail. This makes for a very solid support. It's basically a bridge beam set up between bearing structures. What is hidden (yellow) are short cross beams between the long beams. These sit underneath the seat pan and bridge between the long beams. The black seat rails sit on these cross beams that you cannot see. This structure builds a double 'H' pattern of supports for the black seat rails.
