Hi Brian

Having written my last message it occured to me that I could probably work a solution using geometry - see attached .3dm file, which works really well

Take a spiral from your original script and extrude it down to a point, then revolve a curve (to give a lense fisheye effect) and then use curve - intersect for the result

Going back and adjusting the revolved 2D curve gives a real time visual intersection so you can visually adjust to suit your requirements :-)

Best wishes

Andy