Sure. I just use one in my gun though and carry one in my admin pouch. I like to trim as much weight off of my gun as I can. I know 5 ounces does not sound like a lot, but I save that 3 times and that is almost a pound=)
The main problem with running a battery in the front and back is running the wires past the gear box. There has to be a wire from one battery to the other.