We have not changed the height of Flexslider. Flexslider has three slider layouts,
2. Full Width
3. Full Width Big
In Corporate 2 example, we have used Full Width as Slider Layout. Please read the recommended image dimensions from the readme.txt i.e.,
Slide Post Standard: 940 x 450
Slide Post Fullwidth Big: 1920 x 800
Slide Post Fullwidth: 1920 x 450
You may upload Big image 1920 x 800 and remaining will be handled by Farad, but i will recommend to use recommended dimensions when you are planning to use particular Slider Layout so it will be helpful to,
1. Design your slide image perfectly.
2. Size will be reduced.
3. Results will be 100% as expected.