The best way of choosing is in how you want to decorate your tank or where the tank is located in the room. For a tank with a rock pile in the center, a center overflow is best because the rocks will help hide the overflow. If you are going to have a show piece of driftwood (etc.) in the center, you wouldn't want a center overflow to distract from the decorations, so dual end overflows would be ideal. If the tank is a "peninsula" tank or room divider, a single end overflow perpendicular to the tank would be the best choice.
My 2 AG tanks are not drilled for an overflow... I am using canisters at the moment and really like the clean look of the Megaflow and thought...
Why can't I just get the black plexi covers from AG to use to hide the "gear" in the tanks..? I just asked my LFS if AG will sell just the overflow cover peices...
Now I am wondering if a local plexi shop could just produce them.... and would it be less than AG would charge...?
Anyone ever pursue this type of use before...?
PS/ Any glass tank I get in the future will come as a megaflow type setup....