Hi,
I'm using Windows 8.1 with IE11 on a Dell Latitude E6510 with an external LG screen. I use both screens in my daily work and when I move a IE11 window from the internal screen in my laptop to the external LG screen, the scaling in IE11 changes and gets smaller. It happens when the windows is halfway over to the external screen. On the way back it changes again and gets bigger. I've use the "One scaling for all my screens" in the Control Panel|Display applet without success. It's only IE11 that has this behaviour, no other programs does this.
Brgds Jonas