Here is a top shot of my overflows. I was going for the look of one big rock against the back wall with the overflows sticking out the top of the rock. Each overflow is 6" clear PVC pipe and they are about 10" deep. I hot air welded a PVC bottom and a 3" coupling onto the bottom of each 6" overflow. The drain side of each 3" coupling is glued, The top side of the 3" couplings is where my Durso stand pipes plug in. The Dursos are not glued in, so I can take them out to clean them.
The piping from my supply pump goes up the back wall, above the water line, and
then back down and into the supply bulkhead inlets in the side of my DT. The reason for that, is so I don't have to use a checkvalve, to keep my entire tank from siphoning into my sump when the pump shuts off for any reason. Checkvalves get sealife growing inside of them and eventually fail. The two 1/2" ball valves in the middle of this photo are for siphon breaks. The black 3/8" tubing attached to them spray a stream of water into my DT just below the water line when the supply pump is running. When the supply pump shuts off, those 3/8" tubes draw in air, breaking the siphon. There is probably a small amount of flow that I lose, due to friction loss, by running my supply piping up and over like this, but so what, I would rather not have any floods. I also oversized my supply piping to 2" to make up for a lot of that friction loss.
The two other ball valves in this photo are for a locline supply and a OM squirt. Both of these supply water to the top of the DT so even if my other siphon breaks where to fail, because they where for some reason clogged, these will also act as siphon breaks. I've never had the 3/8" tubes clog so far in 4 years, but I like having two siphon breaks on each supply just in case.