I'm not sure I understand what point you are trying to make. The fact that when a boat completes her tack in the zone from port to starboard and is either clear ahead or overlapped to leeward, that boat does become the Right-of-way boat.
Can the port tack boat tack to starboard in front of the original starboard tack boat requiring the original starboard tack boat to alter course or give room for the just tacked boat to clear the mark?
The answer is "It depends"
If the original starboard tack boat is fetching the mark and can sail up to close hauled to avoid and keep clear of the new ROW boat, she must do so. Rule 18.3 limits the new ROW boat from forcing the original starboard tack boat to sail above close hauled or from passing the mark on the correct side.
The ISAF rules committee removed the Old Preamble to Section C rules to make the rules easier to understand.
Remember the first rules you must be concerned with are Section A rules! Then check Section B,C & D rules for "Obligations or limitations" to the Right of Way boat from Section A.
In Skip's question, The new ROW boat, if she had completed her tack, would break rule 18.3 if she causes the original starboard boat to sail above a close hauled course to avoid her. The ROW boat does not break Rule 18.3 by forcing the original starboard boat to luff up to a close hauled course to avoid the ROW boat. It is important to remember that the original starboard boat does not have to anticipate or take any action until the port tack boat has completed her tack. If the new ROW boat tacked so close to the starboard boat that the starboard boat could not avoid her, the ROW boat would have broken rule 15, If the the port tack boat completed her tack clear ahead of the starboard tack boat, rule 18.3 stills limits her rights as does rule 16 if she alters course after tacking.
Your first statement:
<font color="blue">"In your example Skip, if the boat tacking in front of you was able to complete her tack, regardless of if she slow to pick up speed, she is the ROW boat." </font id="blue">
Your are right, she becomes the ROW boat, but you must also consider the limitations as per Section A Preamble. In Skips question. The boat that tacked is subject to Rule 13, 14, 15, 18.3. When she arrived at a close hauled course (Think of this as a compass course and nothing to do with the sails), she must THEN allow room and opportunity for the other boat to stay clear. If this tack takes place in the zone, Rule 18.3 further restricts the ROW boat by not allowing her to force the other boat above a Close Hauled course to avoid her. Cases have stated that the other boat has no obligation to anticipate the the boat that tacked would break a rule, like rule 15 (not allowing room and opportunity to keep clear when she completed her tack).
Your other statement:
<font color="blue">"Lets say that she tacks under you and then shoots the mark. Again, she is able to do this under the rules and you must keep clear as long as she completes her tack." </font id="blue">
The boat that tacked will be the leeward ROW boat but can only shoot the mark if she does not force the other boat to sail above close hauled and complies with rules 15, 16, and 18.3.
Your last two statements I agree with.
If you read the rules the way they were written, you will see how they fit together. ALWAYS determine the ROW boat using Section A rules first!!!! I can't say this enough. Section A rules apply throughout Section B,C, & D rules. You will find that there is a time when Section a rules are turned off, like Rule 19.2c, and in the Pramble to Section D rules. Once you have identified the ROW boat, find out if Section B,C & D limit the ROW boat.
To answer you question, Rule 13 is talking to a boat that is tacking, it does not care if the boat is tacking from Starboard or from Port.
Rule 13 and 18.3 only are taking to the boat that is tacking and the other boat, not to a port tack or starboard tack boat. You will also note that as the starboard tack boat completed her tack and became the ROW boat, she now has the limitations of Sections B,C & D. Rule 15 requires her to provide room and opportunity for the other boat to keep clear. Rule 18.3 also would apply to the ROW boat if they have not passed the mark and if they have passed the mark and still in the zone, you would go back to Section A rule that would apply and again, any limitations such as Rule 16 (Changing Course) or Rule 14 (Avoiding Contact).
I hope this answers some of the quesions you guy have.....
I recommend Dave Perry's book "Understanding the Racing Rules of Sailing" Page 168 covers just about all of your questions. Good graphics too!