"Mini-guide" for the updated version.
Locate your "xgcore.dll". Make a copy of it just in case and open it in your favourite HEX editor.
Then search in the hex editor for the hex values: 39 8E E3 3F
And replace them with the values for your desired aspect ratio, for example: CD CC CC 3F (16:10) or 26 B4 17 40 (21:9, 2560x1080).
I did it with my updated game (1.10.02) and there were a total of 5 values to find and replace.
For more values, always look in:
http://wsgf.org/article/common-hex-valuesThe very first table is the one you need.
Cheers