I put the calfo on one end, and my 18gph return on the other end. The entire surface sheet gets replaced every few seconds.
Make sure you have enough room between the calfo and the front and back to get a cleaner magnet in. I just "parked" my cleaner magnets at the calfo - and you don't even see it.
Yes, size your drains so that they can handle 200% of the return flow, AND make them redundant. In other words, 4x your expected return. As your tank ages, your flow will slow a little, and then a turbo snail will get caught!
Bill
215g FOWLR... and anemones, GSP, gorgonians... carp, that isn't FO!
"I killed my first SW Fish in 1971..."