I use a 3440x1440 monitor and found it helps to raise zoom from 0.5 to 0.7 or even a little higher. I find this minimizes distortion on the sides and in addition the view is closer to a natural one.
However, be careful with too high zoom values as those may incure a performance penalty.
I doubt this works for an aspect ratio of 48:9 of the OP, though. Plus, I agree the lens correction in the menu does virtually nothing.