jcl confirmed that the engine 'assumes' 3/4 ratio, but only in fullscreen, because it makes no sense in windowed mode.

so whenever you enter a custom resolution you have to set the view.aspect not to the aspect ratio itself but with the above formula thats good to know.

so noe to get widescreen working you have to follow the steps:

-get current windows res.
-find out wich aspect that is.. (16/10, 4/3, 16/9...)
-set a widescreen resolution
-set the the view.aspect to the above formula but only if you are running fullscreen engine