[framerguy]

That 3"wide x 4"tall x 48" wide trough goes from end to end (ie:coast to coast). In the corner (or in the middle, or where ever you want it) there is a smallish box, say 6 x 3 that runs the height of the tank. You plumb that area the same as your other overflow would have been. The return pipe is hidden inside the coast to coast and piped out either end. You don't really lose anything you would have been using anyway.