Currently I am running a 96 x 36 x 30" tank (24" longer then the proposed tank) housing four south american arowana 27-30" long. This tank is crowded, was much better suited for just three arowana. So trying to house 5 of these monsters in a tank 3/4 the size of mine is crazy, actually the 6 foot is too short to house any aro over 24". Can't really comment on the rays, though 2 does not sound bad, no experience myself.
Blueberry arowana 