Well mate, glad to see you get these stable at 2GHz too. Can you flash SPD with XMP and test if both 1866MHz/2GHz XMP profiles works stable on Rampage Extreme without messing with any settings in bios?
GTL settings are not universal, they depends on what PSU you use, even what revision board/what fab(for asus ch/tw) it is manufactured. So this is trial and error process. I have P5E3 Deluxe to test later on.