I'm using the Autoaqua smart ATO micro. It works very well. The ato Resevoir is below the stand, it comes with a submersible pump. The censor is in the middle section of the back "sump" area, where the return pumps are and the only section of the tank where the water level varies. The water line from the pump can be placed anywhere in there back, or even in the display area for that matter. I can take pictures for you if you'd like.
The skimmer (Aquamaxx hob-1) has an intake and return pipe, the intake is in the first chamber, which also houses the overflow and media basket. The output goes into the second chamber. Normal water flow goes between chambers 1 & 2 UNDER a baffle, the skimmer is carrying water over the baffle.
The sides of the "sump" are the same. 2 overflows, each side has a chamber 1&2, then flow over a second baffle into the center "return" section.
It's a great tank IMO, I'm a noob but I highly recommend it.
Still have a micro bubble problem, but I've designed a diffuser that I'll be making tomorrow at work, so that should be all fixed up soon.