shut the door

From our illustrious forums…
Hi, so quick 18.3 question for racing in strong current. We are Starboard (S) inside the 3 boat length circle, but everyone is overstood because of the current. We are bearing off already to fetch the mark. A boat (P) comes in on port below us inside the circle and tacks to starboard inside of us. P is now also fetching the mark but tacked inside the 3 boat length circle.
Can we ‘shut the door’ on him and keep him from rounding or do we have to give him room even though he tacked to starboard inside the circle? To give him room we would not need to go above close hauled since we are overstood (due to the current).
Jump in the thread for input.