I'm not quite satisfied. 😉
First, an aesthetic comment, change the settings of trace #7 to "dot" and "draw". I think it looks cooler. Maybe not... It is subject to one's own opinion.
Second, you seem to have KNOWN (almost as if by magic) where the chart limits should be. Can you generalize the chart limits to show the desired region?
I would guess that you have to solve all the intersection and pick the greatest in four directions.
Careful! Some pairs don't have intersections. Worse yet, an existing intersection could be very far from the desired shaded region.
Third, WOW!