First, navigate to Uncrewed in the Steam files. For those that do not know, it should probably be in Program Files (x86)\Steam\steamapps\common\Uncrewed\.

Once there navigate to System\App\Bin in Uncrewed. Find a file called "default.xml" and open it with note pad (or any other compatable text edditor). Within default.xml you will find windowed="1". Change the 1 to a 0 and save the file. When the game is next started it should launche in full screen mode and scale properly to the size of your screen.