@MFerg: The height depend on the featured image that you have added in your posts. Our recommended featured image size for the slider is Width: 1280px and Height: 550px. So, all the image uploaded in this size or greater then this will automatically crop into this size and will be used in slider.
Now, if you want to reduce the height of the slider. Then you can upload the image with smaller height then 550px. In this case our slider code will not crop the image and will show the original image size you have uploaded. This will reduce your slider height.
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