Can the video be shown full-screen?
Well, that’s always a possibility, but remember the main point of the video is to raise interest and awareness of your message, the copy around the video is important too, maybe even more important from a business point of view. If you run the video at full screen, your target audience will quite probably watch the video then close it and move on. With the smaller video size I recommend your target will begin looking at the copy while watching the video and continue reading after the video has finished. Small is beautiful!