Just got my Surface Pro 2017 Edition today. Of course, have to put some good ole games on it, but would love to enjoy fullscreen when possible. I've been trying to get the custom resolution launch parameter to work to no avail, until i tried 16:9 or 4:3 resolutions only. Then the game happily ran in my requested resolution.

Surface Pro is a 3:2 monitor, so 16:9 gives black borders on the top and bottom. 4:3 gives borders on the left and right.

These arent deal breakers at all; 4:3 with the Surface Pen is really nice. That direct manipulation of the game world feels "right". But boy howdy would fullscreen be nice.

OpenGL flag is a no-go; that forces the game to run in a very tiny window locked in the upper-left corner of the screen. Have to use Task Manager to force quit it.

Can anyone confirm that 3:2 resolutions aren't supported? Maybe someone has an idea about how to get it working?

UPDATE SOLVED:
For reasons i do not understand, though the Surface Pro has a native 3:2 aspect ratio, checking Settings > Display > Display Adapter Properties > Adapter > List All Modes shows no additional 3:2 options. Using 1440x900 gives an almost fullscreen experience while also drawing the UI at a pen-tappable scale. Good enough for now.

Well, could you give an example of the resolution you were trying to run it in?

Yeah, 1350x900 was what i wanted.

COMPLETELY SOLVED:
Surface Pro has an Intel graphics chip but does not come with the Intel Graphics Control Panel. This can be manually installed, allowing low-resolution games to once again scale to fullscreen, as God intended. (solves my Baldurs Gate issue)

The big important tool this control panel brings to this issue is the ability to define custom resolutions. By adding a few 3:2 resolutions at 60hz, then restarting to let the display adapter see them, i can now define a 3:2 custom resolution of 1350x900 (although the Intel control panel apparently wanted 1352x900, as it auto changed that x value without prompting)

Fair enough; I assume that the SC4 engine was not built to naively handle it.

Hmmm, perhaps. I think the main issue is how the graphics driver doesnt report any 3:2 resolutions to the system. SimCity asks for the resolution but is informed that the system doesnt support that resolution and so simcity just falls back to the next closest supported resolution. Once i taught the system of an additional resoution, simcity is happy to use it without issue.

In short, i blame Microsoft. lol