Something I've been playing with since i first got the dual is shifting the bed fan around to the front of the machine (like on the singles) to direct the cooling more equally at both nozzles. This simple fix cuts way down on oozing issues with the left nozzle while dual printing.
It worked fairly well for the first attempts, and did re-direct the air flow very well, but the fit was a bit loose.....I wanted to shrink the hole a little bit so that the first time you screw it on, you self-tap it. (Tighter fit.)
Anyway, I've fixed it up and it works a lot better. This one works with both the original M2 dual and the new Rev.E dual M2s. It helps with the left nozzle ooze.
(You will need to carefully remove the little bit of glue that holds the wires into the side fan slot and remove them from the hook to give yourself enough slack to reach the screw hole. Don't pull the wires out. 
)
File's here:
http://www.thingiverse.com/thing:1163035
