I have to confess I cheated.
I drew a fill block on the floor plan and saved it as a object.
I created it at the origin to a known size (600×600) using a fill geometry ‘linked to the fill origin.
I then selected it and saved it as an object, opened the object and edited the 2D script.
I can go into more detail if that would help but I’m not sure how much you know.
Let me know if you need more guidance.
Hope this helps
16Gb RAM 500Gb SSD