God that red grid on that green background just killed my eyes. Anyway i also played around with this, and ended up with it's cant be done properly.
As you can see whitin my awesome photoshop skills i think blizazrds settexcord function can't handle properly when you edit all the 4 corner's coordinates. Most likely because it's doesn't start the torsion from the image's center, but it's topleft and bottomright coords.