I'm planning a 7'x4'x30" build in the next few months. I will be buying new glass from a local shop here. I believe 1/2" will be suitable as I saw uaru Joey do his 6x6 build using 1/2". Just wanted to get some more opinions.
The water depth to the top of the glass of my current tank is about 29 inches also, with no problems with the glass for the last 3 years. I felt very nerves about it when I first built it. But I think it has proved its self by now.