Drew, when a windward boat overtakes a leeward boat and creates an overlap from a position of clear astern, RRS 17 does not apply between the boats. 

Assuming no other issues like obstructions or marks around, the 3 rules in play are RRS 11, 14 and 16.1, none of which have any reference to "proper course"

So the answer to your question is "yes" a leeward ROW boat may still luff under the 2025 quad, as long as they abide by 16.1 and 14. 

Im confused. Rule 17 specifically mentions not sail above her proper course. "If a boat clear astern becomes overlapped within two of her hull lengths to leeward of a boat on the same tack, she shall not sail above her proper course while they remain on the same tack and overlapped within that distance, unless in doing so she promptly sails astern of the other boat.” to me that sounds like rule 11 is switched off rule 14 applies 16.1 would apply the leeward boat could slowly turn up but not aggressively. Surely 17 implies the leeward overtaking boat cannot luff the windward boat? or am I missing something 

sorry I misread your comment. Understood windward overtaking has no rights and cannot call maintain proper course to leeward overtaking boat. 

And equally, I don't think the situation has changed much, if any from last year. Of those four rules (11, 14, 16.1, 17), only 14 has any changes at all, which will minimally if ever affect the situation.
Drew Scott, it would be instructive for you to read RRS 17 in it's entirety and diagram for yourself a few situations where it does and does not apply. It's only the one sentence.

Niko .. re: "Of those four rules (11, 14, 16.1, 17), only 14 has any changes at all, which will minimally if ever affect the situation."

17 has changes in 2025

Drew re: "Understood windward overtaking has no rights and cannot call maintain proper course to leeward overtaking boat. "

Importantly, if you change the scenario such that it is the leeward boat overtaking from close clear-astern, and 17 applies, there is no "call" to a leeward boat of "maintain proper course".

If you are the windward boat and the leeward boat starts to luff you, you as the windward boat must respond and keep clear.   Your only recourse as the windward boat is the protest. 

Never, never, ever hold your ground.

If you think the leeward boat is sailing above their proper course, rule 17 entitles you no room and thus no exoneration for breaking rule 11. 

Keep clear and protest. 

"Keep Clear and Protest"

Is that the Protest Committee's version of the T-shirt ... "Keep Calm and Carry on"?  :-)