I read on the Dev's main site him saying it's possible to stretch the screen in-game so that it's not
a tiny box. (Though it's not recommended)

I've been digging in the Smugglers V Invasion folders, the main one and the one in My Documents,
but am not sure which file to edit, the name of it or whatever.

Any help appreciated.

Looks like he actually says 'Windows display settings' I wonder which ones?

Dev's Quote:
"The original option in the game to change the resolution of your PC has been removed, because it caused confusion. If you must, you can do so in the Windows display settings. It´s just not recommended, because the artwork looks better in your native resolution and you need the additional space at the side."