Just create another model with those duplicate nodes. I think it was decided, after Sean looked into the code, that models to the right side of the grid overlayed models on the left side of the grid at the same timing mark.
So you can have a model of window tops and window bottoms. Just draw them close to each other in the visualizer and you can do what you are after.
In LSP we do that with Layers and only have to draw the model once.
Alan