Sorry if this is a repost, but I figured out how to run the game in an ultra-wide resolution.  I noticed that when you click 'Back' on your mouse in 3DMigoto it hides your GUI completely, but it also exposed areas hidden by black bars to retain the 16:9 aspect ratio.  This is interesting because there are no ultra widescreen resolutions, but the extra areas are being rendered anyways.  After hunting around for a while, I found a pixel shader that allows you to hide the black bars on either side.