When I ride on a section of highway there is a nice shoulder that I take. However I make it known to passing motorists I own ALL of the shoulder up to the edge of the white line. Often I will weave back and forth drifting over to the edge of the lane when I can hear that cars are coming but are not very close, then drift back to the center of the shoulder as they pass by me. Usually they will move over to the second lane away from me because I look somewhat unpredictable. No one wants to hit you even if it seems that the way they are driving appears otherwise. Do all that you can do to be seen and try to become a fixture in their thought process.