How can Green defend against this? The key is anticipating Red before it makes its move. The simplest thing is Green pulling in its mainsheet to slow down. With an overlap, Red cannot bear off because it is the windward boat. Green slowing down is one of the few times when it pays to not to sail your fastest. In this case, Green should slow down enough to let Red get even or slightly ahead. This prevents Red from digging in, Green wants to make Red take the widest circle possible. Green should also consider jibing before the mark, being careful not to touch Red’s boom, to give Red more to think about when rounding.
Green’s best option is to anticipate this and head up and make eye contact. This sends the message “I’ll take you off the course if I have to.” This is a good move in fleets where Red is more likely to not waste time with just one boat. Alternatively, Green can let Red get and inside overlap and hope to get inside Red after the rounding.
Another option is Red being very aggressive by using its luffing rights outside 3 boat lengths, but luffing will waste many boat lengths to the fleet. But Green has a good defensive move that it can use.
In this third scenario, Green has jibed onto starboard. This means that Green has all options outside three boat lengths, including heading up and forcing Red away from the mark. Green’s best move would be to slow down outside three boat lengths to force Red to take a wide rounding.
Red has a few options but has to anticipate them well in advance. It could jibe and then exercise its rights in the first scenario. It could also bear off and hope that Green’s jibe mark rounding is wide enough to dig inside.
With an understanding of these basic strategies, it is possible to use mark rounding to gain significantly during a race.