TJ - Another thing to take into consideration when placing diffuser stations is that they will help keep sediment that is brought in by your streams suspended in the water column if they are placed too close to the mouth.
If your streams bring in moderate to high amounts of suspended particulate, and you place your diffuser stations too close to the mouth of them, particulate that is suspended will be kept in supsension much longer by the uplift and circulation of a poorly placed station, and add to any clarity issues you may have, or present you with a clarity issue if you don't already have one.
I would stay out of the stream arms. This will give suspended particulate more time to settle, instead of being circulated into your pond's main body water column.
