Support for cinescope resolution for the GUI? 2.35:1?

I have a cinescope screen (2.35:1) and I’m looking to see if I can get the GUI to take advantage of the full screen. All the resolutions are 16:9 format. Is this something that would be done in the basic display settings for adding a custom resolution, if it’s supported?

Would the skins have to have support as well, or do they just operate based on whatever the display resolution is set to?

Has anyone tried to use one of these boxes on a full cinescope screen?