here is a poor diagram of my overflow, external durso...shown to me by Darren.
it only utilizes 2 90s.
it is a 1.5" bulkhead, which handles my mag12 return, which goes straight up and over the tank, using a total of 3 90s.
just so you have an idea of what kind of flow i am seeing through the overflow.
so you could certainly use this design on the non-viewable end of your tank. and make a small overflow box, as i did. you could even incorporate a second bulkhead to it.
kinda like this...
