Er? Why? to feed the F 6A?
You can already do that with his hub -- if you do not mind vastly overloading the USB socket, just leave the other port open, plug in the F and crank her up. A dual to single adapter still faces that max 3A limit for the single socket.
Very good point! Totally forgot you could do that on the gekko hub. Just had a vague memory of someone doing that kind of thing in the past but now I think of it, it was probably do get around the per-port limit on a particular hub.