i agree that just making the line between the channel mark and the sunken object an obstruction won't solve the problem, because that line is too short to constitute a continuing obstruction, but it just makes it more certain that the channel mark/starting mark is not surrounded by navigable water, so Preamble to Section C doesn't switch off Section C, and RRS 18 applies.

I agree that defining/describing the starting mark to include the channel marker and the sunken object and the line between them will create a large starting mark which will be surrounded by navigable water, so Preamble to Section C will operate to switch off all mark-room and obstruction rules while starting.

There are disadvantages to having very large starting marks (although once upon a time we used to use whole battleships for starting vessels).  There used to be a whole section of RO training explaining disadvantages of using a large vessel at the pin.  Principally the disadvantage is that it creates a no-go zone around the precise end of the starting line, so at the least the length of the starting line needs to be increased to allow for this.

Welcome Charlotte!  Happy to have your contribution. 

Ang

As a retired IJ and IU my take is that Blue, being a fast reaching multi-hull, is on the cusp of breaking rule 17 at position 6.

I think that wording is quite workable, if that's what you want to do.

Rule 89.2 provides the option to change the NoR provided adequate notice is given.

As brought out by John d Farris, any change needs to be communicated to all stakeholders.