An issue appears to be that a superstring uses 1 channel per colour. I thought that in the past a superstring could be a single channel with multiple colours. It's been too long since I played with the superstring setting that I don't know if it's function has changed or if I am misremembering. I think that if you change your model data to just being 1's and stick with the superstring you should get the result that you are looking for but the visual appearance may not look quite right.
Alternately you could create 2 single channel models each with it's own colour and then create a waterfall group.
Alternately you could create 2 single channel models each with it's own colour and then create a waterfall group.
