Well, you are just "Flow Insane" Amphiprion. I have 1 on my 75G and couldn't imagine even having 2. 1 is already too strong if turned up all the way, granted I don't have a 48" tank either, just a 30". I still have to balance flow with sandstorm/corals getting blasted. Actually, using short pulse mode, I doubt it gets over 30% speed.
I did see that tank before though when searching youtube for videos, but I never saw the entire tank like the video you found, I just found one that showed the 8 vortechs on the wall. I guess it works for him, but I would think placing them throughout the tank would be a better idea, although a more unsightly idea which I am sure is the main reason that person chose the placement they did.