Okay I have also been eyeing this setup from tsunami. Anyone know if they are reputable?
http://www.fishtanksdirect.com/240GallonRectangularAcrylicAquarium96x24x24.aspx
Although it wouldn't hurt for thicker glass (other than increasing weight), I'm not sure if that's needed of a 24" high tank. Usually when you order custom tanks, they typically will provide a recommended glass thickness and rough "safety factor". So I'd go with what the builder advises and pick what makes you think is best given your options.
I have a 72"x30x28 that with 1/2" starphire glass. But also with 1/2" x 4" wide euro-bracing on the top and bottom perimeter. Also 1/2" x 4" glass brace. It seems to be doing ok.