Filling gap between two mirrored objects


For my school project I am required to create a building, however I have a small gap showing. Is there a simple way to fill this gap between two objects which have been mirrored? I am very new to grasshopper therefore I don’t know any of the tricks yet.

I have attached the current script below.


Test File (37.9 KB)

can you sketch how you imagine that gap to be filled?

I would like two corners circled in green to meet at the centre of the red X