Simple question, how do you stretch the height of a video? You can stretch the width using "motion" but you can't stretch height. A google search didn't help me.
Unless you uncheck "Uniform Scale" when you scale up the width you also scale up the height.
If you want to stretch the video out of shape, and most people do NOT want to do that, then uncheck "Uniform Scale" and you will have your choice of height and width individually.