Best way to display out of limit plot points

WPF C#

Hi, I need to somehow mark points that are out of limit on my Graph of 4 LinePlotRenderers.  This is the data structure:

Point[,] dataArray = new Point[4,256];

At the moment I'm thinking to simply add 4 PointPlotRenderers to display those out of limit points (so it total I'll have 8 plots).  But I'm not sure what is the best way to pump this data into my graph.  If I always have the dataArray structured as above (4x256) and points out of limits could be blank, or any combination all the way to 4x256...  What's the best way to pump all of this data into my Graph?  I mean, I can't join them into the same 2D array because size of array of points out of limits is not going to be the same.  if I make it the same by padding with 0s then my Graph will shift to trying to display 0,0.

Does this make sense?  Maybe there's some other way to work with limits?

Thanks