"Arranging fans in series - stacked on top of each other, so one blows straight into the other - gives  no improvement in free-air performance, but doubles the pressure increase in a sealed box, and better and better performance compared to parallel fans as the system resistance gets higher and higher. Incidentally, this means that those goofy monster processor heatsinks with layered low-profile fans are a waste of money, since fans strapped onto a heatsink are very nearly in the free-air situation, and putting two layers of them there does close to nothing to the airflow."  Source

So an array of fans next to each other would move much more air, but the static pressure would be far less (Would fill up the bag quicker, but the bag would be saggy), this is why the bag balloon too a bit to fill up, but then looked like it was about to burst