Looks big for 84 gallons and I noticed you made it only 18" high which has allowed you to use 1/4" plate glass which I believe is much cheaper and much more readily available, smart move.
The low height really saves on the glass thickness. Your project sparked my interest and I found out that you can increase the width by factor of 100% or to 30" for 168 gallons and still use 1/4" glass with a safety factor of 2.5.
Now Im interested in building wide tank like that with only 1/4" glass. But I probubly would go with more traditional bracing so I could fit my standard filters systems. Obviously you have a large sump in mind.