I've wondered why the aquarium manufacturers don't make the support (and entire rim if that's what it takes) out of clear acrylic?
I have a 30g tall (36" long) aquarium that has been in continual use for 15 years. It does not have a center brace. The front glass is ever so slightly bowed. If I hold a metal straightedge against it I can see the bend. Hence "needing" to upgrade to a 75g