Mixer levels, clipping and misinformation

I read the DJTT article (http://www.djtechtools.com/2011/11/1...he-real-story/) which recommends keeping channel and master levels at 0 db, certainly not operating at the meter maximum.

After watching 2 different videos of skrillex (http://www.djtechtools.com/2011/10/0...e-eyes-of-djs/) and (http://www.youtube.com/watch?v=zEhasYA6nVk) at Creamfields 2011 and Shambhala 2012 its apparent he's consistently playing with channel and master levels on his DJM800 at +7 to +11 db.

DJM800 specs rate the standard and rated output levels of the mixer at +2 and +22 db respectively. There is also an option for attenuation of the master from -12 to 0 db. A pioneer representative says the attenuator can be used with DJ's that insist on operating in the red with a setting of -6 or whatever works for your system. A "good" DJ that keeps levels in the green with both channel and master output levels at 0db or less can operate the mixer with 0 db of master attenuation (http://forums-archive.pioneerdj.com/...04/m/528109401). Either situation results in a output level from the mixer of ~0db.

In the case of Skrillex's performance at Shambhala's Pagoda stage in 2012 which has a sound rig designed, built and operated by PK Sound that likely consists of PK CX800 subwoofers (http://www.pksound.ca/wp-content/upl...-Subwoofer.pdf) and PK-VX12 line arrays (http://www.pksound.ca/wp-content/upl...rLineArray.pdf) each powered by a QSC Powerlight PL340 and PL325 respectively. Input sensitivity for these amps can be set to either +26 or +32 db. Assuming proper gain structure, the input level of the amp would be set to balance the output level of the mixer to obtain suitable power levels in the amp. This would indicate that the ideal output level of the mixer has to be either +26 or +32 db.

These two situations obviously contradict each other by a large margin.

My questions are:

1) Is the ideal output level of the mixer solely dependent on the required input sensitivity of the particular amplifiers being used?

2) Does the high rated output level of the DJM800 and the fact that the master attenuation can be set to significantly reduce the output levels post master mean that the meter levels on the mixer do not give an accurate representation of the actual output level or whether the outgoing sound is clipping?

3) If both 1 and 2 are true, shouldn't the sound tech be unconcerned with clipping originating from the DJ's mixer with compressors/limiters just in case and also be able to ultimately control the volume of the sound environment by altering the amplifier gain or main outputs on the sound board. If so why warn or chastise a redlining DJ as long as you do a sound-check and honestly determine if they play in the green or red and make adjustments to compensate? Why make generalized statements advising all DJ's that they must keep levels at 0db or less when it doesn't apply to every mixer and amplifier pair which have different capabilities and requirements? And why don't all sound tech's know how to deal with this correctly and professionally?

4) If 1 OR 2 is false how can a DJ like Skrillex red line a whole set on massive systems without clipping?

5) Ultimately is the answer to whether to keep mixer levels at 0db or less all the time yes? OR it depends?

There seems to be A LOT of contradictory information out there. It seems to stem from the opposing opinions of ignorant/uncaring DJ's and ignorant/uncaring sound tech's. Definitely no easy answers in a sea of misinformation.

Will someone, who actually knows, please clear this up.