Playing Stepmania "Co op"

I was looking to see how I could set up a co op mode like the following video, where two players share both pads and work together for the final score: https://www.youtube.com/watch?v=HI1cNMsCaBE

From description of the video I'm guessing it's just a normal single player doubles chart but the notes are skinned for the corresponding players. Any place where I can browse where people have made co op charts? Or if there is a different way of setting a mode like that up?