I'm not sure, but does the start mark count as an obstruction in this case? If it does, then the leeward screamer can't force you to hit it, and the slow windward boats aren't barging because they aren't causing the overlap. The boat that becomes the give way boat doesn't have to anticipate the situation, but only needs to start responding promptly after the overlap was created. It would be one thing if they were in the middle of the line, then the windward boat would have to come up even if it meant going over the line, but if he would have to hit the mark to come up enough, I say he's obstructed and the leeward screamer needs to just settle for his speed advantage, and not get greedy and try to force an OCS on the other guys....