ZERO comments after 5 years??? That's pretty amazing. Anyway, after following your technique for achieving full screen, I wanted a simpler way, easy to implement inside Web Builder if possible since I update often and don't want to have to repeat and repeat your instructions. My search led to discovering that if I set "Aspect ratio" to 16:9, there is no problem at all. The video fills my 1920X1080 screen; and however I reduce the window -- vertically or horizontally -- the window remains filled with this video. In fact, the video stays full size rather than compress with either the vertical or horizontal window compression.
I looked for an old 4:3 video to test with, but Youtube seems to no longer support that size. The few small videos I found had already been remastered to 16:9. (..by Youtube?) Anyway, seems I don't need to even be concerned about dealing with 4:3. So all problems solved!
