Rule 17 is to be considered when you find your boat coming within two of your boat lengths to leeward of another boat. Once you enter this zone from astern you are no longer able to sail higher than your proper course, which is generally perceived to be your course up until the point that you entered the zone.
This is where people get confused! I have seen both parties adamant they have the right of way. Firstly I have been steering a sports boat approaching a larger more traditional boat. I wanted to sail on a touch further before we gybed away to the mark so I called them to ???keep clear???.
I received a torrent of abuse from the other boat and a very knowledgeable sailor yelled for us to sail our proper course to the mark! I later post-race pointed out to him the error of his ways and explained rule 17 limits a leeward boat that approaches from astern within two boat lengths to leeward to not come above HER proper course.
The windward boat???s proper course is immaterial and is still obliged by rule 11 to keep clear. The old ???mast abeam??? rule has gone the way of the Dodo! I could actually see the realisation dawning on him as we read the rule book. He had been competitive sailing for over 30 years and is held in high regard. He just never kept abreast of the rules.
The correct response if you find yourself in this position where you have a faster, higher sailing boat approaching to leeward is to alter your course to parallel the approaching boat???s course. Once that leeward boat sails up to you and gains an overlap they cannot then luff or sail higher (which has also happened to your scribe on more than one occasion when the shoe was on the other foot).
They are obliged to go no higher than their proper course under rule 12 initially on the approach as they are overtaking from clear astern and must keep clear. Rule 17 kicks in once the overlap is established.

Just saw that we have an S&S34, Wilparina, in this year. Last around the first mark, to be expected as the smallest boat entered.

The S&S34 is an upwind boat. With the forecast winds not expected to get up from the south she will struggle to get ahead on handicap.