I'm sick of seeing weekend warriors on the roads I frequent doing 15mph tucked into their aerobars and staying a foot or two to the right of the double yellow on 55mph roads.
Stay to the right of the lane for your own safety and respect for other users of the roads -- cars, bikes, MCs, farm equipment, I don't care. If you are not the fastest vehicle on the road then move to the right. Hogging the lane to 'protect your right' may be legal, but it's just damn rude to vehicle traffic. A driver that gets stuck behind some asshat in the middle of the lane is going to remember that inconvenience for a long time. Move to the right so they can pass you safely with minimal intrusion into the other traffic lane.
Try to keep your view of the white line between your front wheel and shifter. If it's outside your shifter you are too far over.
Stay to the right. Even if the road is rough riding on the white line itself can be smoother than the middle of the lane.