Yep, I've used the cord, not the mounts.
Works good, lasts long time.
Gives you, well at least me, lots of time to get back home after getting the 1st level warning.
I've put a battery inside and one, perpendicular, under the belly behind the gimbal. I placed it there to minimize the area exposed to the prop wash.
I'm not a fan of sticking things out there where the downdraft is going to create more drag/weight for the Phantom to have to overcome.
It might be pretty, as pictured, but how much harder to the motors have to work because of the air hitting those batteries and the mount?