I have the same question as Nuge in his last post. I don't think anyone answered it, at least so I could understand. nuge phrased it perfect (for me) in his last post.
do you put your pin on the entrance hole of the imaginary line, - yes, but you have to decide where this entrance point is based on where you want the arrow to exit.
or do you put it on the exit hole but on the entrance side. - no, that would not make much sense