Sadly BFL stuff is not easily overclockable. I'm averaging about 715Gh/s from 1 minirig SC and 4 Singles(think 12 singles), but they're *HOT* and require 10x the attention the 9 Avalons do. I have two AC units cooling them(32k BTU) and they still overwhelm the ACs during the day.
How did you overclock your singles to 89GH/s per board?
He didn't, your math is wrong that's all. Minirig 480GH/s, that means 235GH/s from the 4 Singles.