A 5S pack is nominally about 19volts so to get 1400watts it would need to be proped to pull about 70amps, it would be working hard, but would work, you may need to take into account the extra weight of the 5250 mah pack as well, may be a bit maginal in the vertical, I have an AXI 4130/16 in mine on 6S on 4350 mah and its as perfect as I can get on a 16x10.
Mike