This is what I would do, if I was making a Beta tank. I would divide the tank in half, long ways, with a 4' x 18" dark piece of plexiglass, with either small holes drilled, or lines cut, to allow for water flow.
then I would make cuts, 9 inches down every foot, taking a separate 12" x 18" piece with the same holes drilled, and the same 9 inches cut, and make interlocking pieces. Then I would seal them with silicone. I would set the tank up long ways dividing a room (like between a living room and a dining room or something) and position a canister filter, so the spray bar actually runs down the middle of the tank, spraying in both directions down the tank. This would let you have 8 beta compartments, four seen from each room (or each side of the tank.)
If I couldn't use both sides of the 55, I would have a hard time convincing myself to do it.
'Just my thoughts...