The second major consideration was trying to avoid flooding, as much as possible anyway. The 4 main flooding points that I know of are: ATO sensors fail, back flow from return line, skimmers overflowing, overflow clogging and sump being emptied into main tank.
Unfortunately for this setup I had to reduce the size of my sump. With my 38g tank I used a 37 column, since I had a lot of space behind my stand (bookcase catty cornered). Unfortunately that does not work for this tank. I ended up using a 20g tank. I decided that I would only have about 10g total water volume and 10g worth of overflow space. This allows my 5g ATO reservoir to pump all the water in and still have enough space to allow for a 5 gallon back siphon from power failures.
I had glass pieces cut and used the same style of sump I had before. An overflow section that houses my skimmer, this flows to the fuge, which then flows to a set of baffles, ending with my return area. The return area is very small ~2 gallons, but with my ATO reservoir, this is not a huge issue. I was considering a design that had fuge and skimmer on separate sides and return in the middle but I did not do that for 2 main reasons. First and foremost, I wanted as much distance between the skimmer and the return so that bubbles had time to settle. Second, I did not want detritus to build up in the fuge if possible.
I decided to use the AGA mega overflow kit. I could have done this cheaper, but I like the protection it adds from clogging and it was easy .
Here are some pictures of my sump:
Picture from sump level:
Picture from top view:
