Rather than using a script, one can do the following:

From the Menu Bar (TOP) Try WINDOW>Application Frame (instead of Application Bar). Resize your “Frame” to your liking and when you create a new document the same size should come up.

Can use this for documents that are already created as well. After resizing the “Frame”, open your already created file and.. tah dah, to size. Close and open again, and….to size.