This took some messing around with an unwilling Chobby, but it's possible. I guess we could use a better interface for it though. Here's how it can be done:
1. Exit Chobby (The game lobby)
2. Open the Chobby settings file, by default you'll find it in
%userprofile%\Documents\My Games\Spring\LuaMenu\Config\IGL_data.lua
3. Look for the game settings key, it'll look like
game_settings = {
...
},4. Insert the reduced resolution you want the game to run in:
game_settings = {
XResolution = 1920,
YResolution = 1080,
...
},(Replace 1920 by the width, 1080 by the height)
5. Start Chobby again, enter the game settings. Change display mode to fullscreen.
6. Hopefully everything works, in my case it first crashed my OS but worked after a restart.
