I personally would want the tank in 3/4”. “Structurally safe” is somewhat relative to the owner. If you ask a restaurant owner, museum, public aquarium if they consider a bowing tank structurally safe the opinion will be different. I won’t disagree with what’s said as ive personally had 1/2” 500 gallon tanks. 1/2” tank on a 480 gallon is definitely doable and commonly found. For me, I’ll always stick with the 3/4” on a tank that size. If it was 30” tall I would be pushing for 1”. I order enough acrylic to know the cost difference per sheet between 3/4” and 1” is only $50, call the company, talk over the phone vs email. If it’s a custom builder that doesn’t have a standardized price list you can negotiate an extra few hundred cheaper.
I know that marineland/perfecto reef ready Aquarium’s could be considered not structurally safe even though they are made from a structurally safe material thickness. Point being reef aquariums should be calculated using a dynamic load instead of a static load. This is why you see so many marineland reef ready tank failures. Don’t believe me, feel free to google it yourself.
I’m sure you will be much happier knowing you won’t lose your $5000 in stock and $50000 in house damage for saving $1000 on the tank. Go with the 3/4”.
I build and sell plenty of tanks. I can tell you that I build them to the clients request. People like to skimp everywhere. They don’t want to pay the extra $500 for a full top bracing and go with the cheaper eurobrace. They ask for 1/2” material when they should be using 3/4” material.
My advice to you is don’t skimp.