Custom res can give you a major advantage. Doubling the width can increase your FOV stupidly much. The crosshair is kinda fucked up...
Is there any real advantage for this? Naaah, just for fun. But it's always there if someone actually wants to use this.
All pictures are resized to 1920x1080 or 16:9 if you want to know that.
The pictures are taken in 1920x1080 and 3840x1080.
It's my Imgur Album for this...
http://imgur.com/a/updqn#0