I tested this code and the aspection width was to small and all objects looked bad. This is a Problem with to low values.
Here is the code that works better with 16:10 and works also with window mode not only in fullscreen!

video_set(1680,1050,0,1);
wait(1);
camera.aspect = (screen_size.x/4) / (screen_size.y/3);

The wait(1) is to ensure that the vector screen_size is set to the new width and height of the 3D window/screen.