I find that the more I try to squeeze over to the right, the more I have drivers almost bumping me as they go by. Someone advised me a long time ago that if you just assert yourself and take enough of the lane, they will be forced to give you a wider berth. It's worked ok for me so far. Stay visible, make room and wave them past you when there's an opening, and as long as they can't squeeze you off the road, they may do it less often.