I think I am right in my take on this but thought I would throw it out there (slow day on the forum and all):

Two boats on a reach. One boat (L), clearly faster, comes from astern of the first boat (W) and overtakes W and is now leeward of W. L then comes up causing W to come up also. L passes in front of W.
This is legal, under rule 11 and then 17.1 provided that L's fastest route to the finish (this is a long distance race) is to come up as stated, right?
I could be wrong, but there is a friendly discussion I am having with someone about it and thought I would throw it out there. They made a point that the overtaking boat has no rightsat all in this situation- which I understand but it changes with overlap.