I have a widescreen monitor, a Dell U2913WM.
The dual window feature works well for most things, but video streams such as those from You Tube are a bit of a problem since they seem to bypass the Dell Screen Manager and use the full screen rather than the window.

I've tried a couple of "resize" extensions in Chrome and Firefox but could not get what I was after.

I'd welcome any tips or info on how I can get around this.