If you really want to run dual mode, I had it working on Minera on my RPi with 10 Gridseeds. Explained how to set it up in the Minera thread over in the Software section.

End result is your running 2 instances of CGminer-Dmaxl, one is handled directly by the minera interface, the other is just a service in the background. Worked fine for me, I monitored them both via Awesome Miner on my Desktop.