I printed and use Julias Slip in dual fan from thingiverse (http://www.thingiverse.com/thing:1501068) . It works great, especially with flexible filament. But itÂ´s necessary to disable the auto fan mode in z-suite because it will lead to an unexpected temperature drop error message.
itÂ´s simple. If using the nocture fan, cut the yellow cable close to the fan (itÂ´s not necessary). Connect the red cable with the red cable from the lower fan and the black cable with the black cable from the lower fan. All in all itÂ´s a parallel connection. I connected the cable on the lowest level with a solder. But next time I will implement a connector so I can disable the second fan on behalf. The most tricky thing here is, to get the cable out of the metal housing :-)