To help georeference the overlay to Google Earth in Part 4: Add the Overlay to Google Earth. This step will help to precisely position the overlay on Google Earth. Fortunately, the route is available on RidewithGPS in the Google Earth .kml file format. Use the Export tab and click Google Earth (.kml). Now with the route in red on Google Earth, it will be easy to position the overlay to Google Earth.
Ken Whittaker