No, you can't resize it as big or small as you want. It has limited dimensions. It wouldn't expand larger than what was already in the viewer window. I already posted above how you can completely control the size of it using Cast.There is a button next to the full screen button, if you hit it the video will pop out into its own window. That window can be resized as big or small as you want. It can cover the chat from the window that stays behind.