Technically, with
dry air having a dielectric constant of 1000V/mm, you could completely electricute a truck just by getting the electrodes on either side of it.
But, by the looks of the design of that stun gun, it is most likely just two "smaller" 600KV coils; one at either end. The way it is setup you would never have a 1.2MV potential generated, only two
separate 600KV potentials. That's why in the demo pictures on their site you see two little arcs and not one HUGE arc. You could work around this "design flaw" by taking one terminal from either end (one + and one -) and relocating them to the opposite side, respectively. This would allow the unit to develop the FULL 600KV potential of each coil before it fired, and would make two individual arcs across the stun gun terminals. Have fun!!!!