Overflow placement - 1 vs 2 returns?

[reefmandan]

I like option three the best. More returns is better for flow ... especially along the back wall (depending on how exactly you arrange the return flow). I also like three for the placement of the box. The whole idea behind the weir box is to maximize surface skimming, and by positioning the box in the middle, you give more access to surface waters across the whole area of your tank to be skimmed over the weir.