I have a mark 1 supermax 40, which I believed to be the same as an slx, only longer.
Looking at the website I think Dave is right in what he is saying that the supermax 2 is made of a higher grade of carbon fiber. true the mark 1's are quite bendy at reach over connies roofs or velux/solar panels, but I presume the supermax 2's are a bit lighter and stiffer compared to their predecessor.