It depends on the tank manufacturer.
I have my Oscars in a 90 (same footprint of a 75, just taller) and in a 100. I also have seen them in 55's and they can't move around in them. Like MsJ said they need room, more water and more filtration than a 55 because they are so messy. You want a fun fish you gotta pay.
None of this is a problem at all, I was just wondering about the center brace because of "aerobatic" purposes.

The tank I will most likely be getting would be a standard AGA tank.
Thanks again guys!