Same here. No way to set other resoutions than 16:9 in the ingame menu.
I would like to play in 3440x1440.
EDIT: Found the solution. I had to edit the registry:
Screenmanager Resolution Width_h182942802
Screenmanager Resolution Height_h2627697771
Change the according value to your needs.
I had to switch to Decimal though.
Hope it helps...
Post edited June 11, 2017 by oakhill