Fair enough about the quad tracking, Jens Bogren (the engineer of the album) confirmed this information for me.
However also jens informed me that the quad tracking is a layering of amp sound, swapping the amp heads to create te right balace, this will not give you the depth of sound!
However please understand I have been doing this for some time now so i am not that new at it - just not as experienced as Jens!
The phase inversion will cancel out the instruments however this will only occur in mono (hense why this idea is popular as a lot of people listen on single mono speakers -ie Radio and you will notice the center however always remains) - so when you pan left and right the sound is not canceled out, only it becomes odd to the ear, hense why you need a second guitar in the center.
By placing a second guitar into the center of the mix you create what is known as a Mid + Side recording, a classic trick that I would love to go into but do not have quite that much time.
Sorry you have nt heard of this technique but it is popular, more infor can be found here:
http://www.soundonsound.com/forum/showflat.php?Cat=&Number=596976&Main=593413
To be fair my technique is a quick fix for this to work, after all mid (center) = left plus right, side = Left+inverted right, so a mono center + a phase inverted left or right on a stereo pair will produce a simar result.
For the rest of you just try it! Confirm it. If I am wrong and the guitars are normal and just paneed left and rigt then the volume should increase if you play a track of the new album in mono left +right guitar = twice as much guitar volume. However if they are phase inverted with a guitar in the center, only the center guitar remains, with the 2 outside guitar cancelling each other out.
Anyhow no condasending ment, I just wanted to share some advice. It is pretty much correct, but this is due to some assistance along the way.