Looks great! Cool that you had the wheels built -- I've thought about doing that for years.
Iron Pig also has a rear fold & tumble seat:
One word of caution concerning the rear seat: make sure the seat back is high enough. I spent a bunch of money and time sandblasting, painting, and recovering an old Conn-Ferr rear seat, and I am unhappy with the low back. It's comfortable for kids only, and I wonder how long that will last.