Non-Standard sized Background Video

I'm trying to add a background video to a full-width section. I have exported the video at 1280px wide, by 300px high. I set those dimensions in the background video section.

When i leave the section sizing at automatic, it shows the video in what looks like a normal video container, with the 300px high video flush with the bottom, and black space above it - see attached photo.

When I try to force the section height to 300 pixels in the sizing area, it only shows the top black area of the video container in the attached screenshot.

Thanks for any advice you have.