Yea I messed around with the other resolutions in the 21:9 folder, and although doing a smaller resolution shrinks the HUD and healthbars, it also shifts everything out of place on screen. I learned that it's related to these GUI files:
I messaged the creator of the mod to see if they can shed any light, but it's not the end of the world if I have to deal with the long bars. Thanks so much for the quick reply though!