Baseline (Widescreen) Solution & Issues
The game is Vert- out of the box.
GeneralAdmission has released a fix for Hor+ gameplay in all common widescreen & surround aspect ratios.
The archive contains fixes for 16:10, 15:9, 16:9, 21:9, 3x5:4, and 3x16:10 aspect ratios. Instructions are included in the readme file.
Also, I found the camera shake caused by taking damage to be highly annoying, as every single bullet impact would jerk the camera in a different direction. This rapidly diminished the fun factor, so I disabled the camera shake and added that to the FOV fix. Download this if you hate the shake:
Backup C:\Program Files\Midway Games\BlackSite\A52Game\Content\Tweaks\Coalesced.ini and replace it with the fixed one pertaining to your desired FOV.
Fix available from the PC Gaming Wiki Community Files (search there)
Ultra/Super-Wide (21:9/32:9) Specific Solution & Issues
Same method. The fix contains now files for 21:9 Resolution - see Attachment.
Eyefinity / Surround Specific Solution & Issues
Same method. The fix contains files for 15:4 and Wide TripleHead.
4k UHD Specific Solution & Issues