I usually judge my road position by the lefthand stripe rather than the righthand stripe, just as motorists do. Most of the time I like to be a good car width right of that stripe, so cars can pass me without swerving. If the lane is very narrow, I try to position myself so they can go around me while swerving only a little into the next lane. This way, it seems like both the motorists and myself can feel safe and unimpeded. I believe that Forester also recommends similar placement.