This is what I have seen. It is more of an evolution of the arms over times. The V1 arms had the CF rib but it was level or almost level with the arm. That is why the SeaCraft arm stiffeners would work. They also had solid copper leads. The later arms had an extended CF rib and silicon multi-strand leads. SeaCraft would no longer work on these arms. Then the last iteration is the Evo arms. Which appear to be much stiffer.
