I don't know the answer, but 4 12" braces on an 8 ft tank sound like maintenance hell.
All of my 4 ft tanks have had one brace, which translates to 3 for 8 ft. the 30" deep tank has one glass brace, 10". the shorter tanks had a wooden or plastic brace, and I've had 2 of those fail. the plywood tank was repairable, the plastic trimmed tank was replaced.
If I was building a new tank, id be considering a euro brace. I didn t like those at first, but I think I've come around.