I prefer to have the overflow centered (left to right) on the back of the tank. If you're going to have it on the side be sure there is enough room for the overflow box to fit.
I also prefer the center of the back of the tank. I had a corner overflow once and the side of the tank did not look as clean and was more difficult to maintain.
I'll have plenty room for a mag cleaner to get between the box & side wall.
I just think that the two should be at opposite ends from one another. Know what I mean? Then I'm not just sending the return water right back down the overflow.
I like center too with a split return, one in each corner. I wouldn't lower the return as you will have backsiphonage problems to the sump when power is off, keep it as high as possible since it will determine the tank level in a power outage.
Is there any performance reason for the box to be in the center? Or is it strictly a personal preference?
I've actually raised my return a little more. Back siphon reasons. 20g sump, not much room.
With one return your thoughts on having the overflow at the opposite end is probably best performance wise since it makes the water travel the longest distance across the tank to the oveflow and fewer dead spots. I prefer the dual returns myself so you eliminate even more dead spots, much like having two powerheads or wavemakers and having the flows converge in the front center. With this format the center overflow then makes more sense.
I feel for asthetic reasons the center oveflow makes sense since it is easier to hide or at least less noticable and can be hidden behind rockwork or eventually corals. When it is placed close to a corner it impedes on your view from the side.
Is there any performance reason for the box to be in the center? Or is it strictly a personal preference?
I've actually raised my return a little more. Back siphon reasons. 20g sump, not much room.
I'm not sure which MP10 setting you're planning to use. If you want a standing wave in your tank then the center overflow is key. The wave created by my wavebox would wreak havoc on an overflow positioned in the corner of the tank.
Wont be doing no wave action-lol. Nutrient export has worked well on my 26g.
I just saw another 40b setup exactly like I'm wanting mine. With the box on the opposite end, it looks really sweet! Entire center of tank is open-nice!