Cheers, Mike... a pleasure to hear from you
Building this tank without cross braces will be rather easy. What saves you is the height at only 24" tall. Over 28"... and especially over 36"... on even narrower vessels requires scary thick (often laminate) panes.
In this case, you may literally be able to construct this aquarium with 1/2" glass if you are willing to cap the corners with triangular plates... or... band the top and bottom (anodized aluminum or epoxied steel). The banding is simply known in the public aquarium biz as a "four-sided capture". Still... that is not necessary at all for a tank this size.
Are you going to have the Calgary folks build it? Inter-American? Whoever you choose... if they are experienced, they will see no problem with a 4X4 that is only 24" tall.
If you feel very frisky, you might even have them laminate white glass (starfire). It will be more expensive, but even better glass clarity and the laminate thickness (2X3/8" glass for example) may even spare you any stringers or caps at all.
You really have many options... no worries, this will be easy for your builder. And choosing glass over acrylic really will cut down on the need for interfering braces/trim.
best regards,
Anthony