I just recently bought a Dayton 12"DVC from a friend in our forums. I found the T\s specs for the sub and punched in the numbers in WINisd to build a new box. From what the graph shows me, a ported box about 3.0 squft would be the best for this sub. But the graph also shows a 6-7dbs drop around 28hz. How accurate is this graph? Is the slope down, that dramatic?