Dexter you have forced me to upgrade my 10GH/s sawhorse juryRIG monstrosity.
I thought your rig was so cool that I showed it to .... wait for it .... my wife.
Her response was "Why don't you do that?". DOH!

One question. What are the specs on your AC unit? I assume it is a dedicated unit not used for the rest of the residence. I mean if you are pulling 12KW at the wall that is >40K BTU/hr which requires some "real" heat transfer.
The AC Unit is a Mitsubishi R2 Series Outdoor Unit PURY-P200-300YHM-A with 2 x 14 KW cooling power 4 Way ceiling cassettes PLFY-VBM-E
http://www.mitsubishi-electric-aircon.de/eng/citymulti_uebersicht_innen.phphttp://www.mitsubishi-electric-aircon.de/eng/citymulti_uebersicht_aussen_r2.php#wrThis Unit only cool with each ceiling cassettes one cluster a secondary AV unit cool down the room (size 30m²)
If it is under 5 degree out side (at night or winter) additional Fans will cool down the room with fresh air the max low temperatur is fixed to 2 degree inside