Downscaling and Maintaining Aspect Ratio in Desktop/Games

[VoodooPoet]

So I've been playing "NieR: Automata" which does have some support for triple-monitors. If I play it at the resolution set up through EyeFinity, which after bezel compensation is 5936x1080, the aspect ratio is fine. All the circles are circles (not including the UI but I'm holding out for a decent mod for that one.)
The problem is, my graphics card isn't up to snuff for that kind of resolution; currently got a Radeon HD 7870. There are some other settings that are sort of triple-monitor friendly but they're way off; circles are all stretched and whatnot.
The game is lacking in actual config files so I can't attempt to go in and change the resolution it's reading myself, but I wanted to try and take things down to 720p or 768p, which I guess would come out roughly to 3957x720 or 4221x768.
I can't find these resolutions in my display settings or Eyefinity settings, let alone the game settings. Is there a way to manually adjust my resolution to these, so I can bask in the glory of a playable triple monitor gaming experience with the gritty resolution of an Xbox 360? At least until I upgrade my GPU.

[suiken_2mieu]

Read my guide here: http://www.wsgf.org/forums/viewtopic.php?f=66&t=25372