Overflows. Internal or External

[lastlight]

My external overflow on my 400g was no more than 6" out from the tank and I had 1.5" bulkheads inside it. I didn't read the entire thread but 11" seems excessive no?

My current overflow is internal. The box is only about 4" in length from the back of the tank and it only goes down about 8" I believe so doesn't affect where fish swim too bad. Then my pipes exit the back of the tank and 90 down so you have a thin box in the tank and the tank only stick out from the wall the depth of a 90 fitting.