Shodox
maybe water is heavier... sorry but no. Glass is glass and the method of manufacture changed about 35 years ago but other than that no.
For years people have got away with useing thinner glass more out of luck.
The stress that the glass is under is extreame and now days people are more aware of this and want a bigger safty margin built in. The largest tanks I have ever built (and I have built thousands) is 3 fters because Im not confortable building larger tanks with out useing saftey glass as I know what the mess will be like if the tank gives out.
Inh the glass industry, the use of saftey glass has become a lot wider in the last 10 years.
10 years ago, you didnt need saftey glass in showers or 1 panel doors but how many people would feel as safe now days with out saftey glass in those areas. Yes I know that there are still a lot of homes that dont have saftey glass but to be honest, they are simply time bombs waiting to badly hurt someone!
In answer to the question, Yes, pay the money (probably about $10) and put 2 braces on. It may not need it but for $10 plus the adhesive you will have a stronger tank.
I didnt notice if your in Auckland or not but hell, get in touch with me and I will give them to you if you come out and pick them up.