The Newgrange cursus is only about 100m long and 15m wide, but erosion and ploughing out could account for that.
..but surely you're an expert in curses, 4W?
(very lame, sorry. barely worth typing)
Not sure ploughing is strictly possible on this one, its on about a 45 degree slope. There is an EH report out about cursus either now, or later in the year...