It held up 24 inches of water before, so it should be able to now, especially because a plywood tank will be easier to brace.
I would suggest going deeper. Not top to bottom, but front to back. Some monsters require larger footprints and even without monsters a larger footprint tank is easier to aquascape.
Maybe 32 inches front to back? That would allow some monsters in there, and good enough space to work inside.
I with that glass, I would shoot for 96x24x32, this would be a great ray tank! Let me guess, flowerhorns?
With the dimensions I have given you would have about 320 gallons of water. I would do a standard plywood tank (with studs on the outside and rolled insulation+a plywood skin if you wanna save on heating) and coat with pond armour. For the corners and any joints I would use fiberglass cloth to help with strength and sealing.
Good luck with this tank, I am looking forward to how it turns out!