Ok guys, thank you. "Proven in use" is always best. I'm constantly amazed by people's ability to speculate (including my own)!
What about a "rule of thumb" that says the cerges works best with a flow of "fill in the blank" GPH? From what I can see a relatively low flows best: 150gph -- and that is in synch with what disgo says above and what has been said elsewhere on the thread. The exception seems to be when a 20" filter case is used when it looks like a higher flow may work. What do you say?