All rules are fair game at any time. If you discover that someone lied about their entry (say they were bragging at a mid-event party that they weren't a member of the required class), you can protest at any time during the event.

Obviously, it would look best for you to protest immediately upon learning of the infraction. But sometimes, people are warned and given a chance to make a correction. If they choose to continue to break the rule after being warned, they should be protested.

Having said all of that, I think there is another way to look at this whole thing. It could very well be that the sail material concern was well known in advance, and the OA, PC and IJ decided the rule infraction wasn't a major issue, and they weren't going to let it become one during the event.

The timing of events makes much more sense under this train of thought, no?

Mike