Hi,
Here are two videos of mine:
http://www.youtube.com/watch?v=vu5IMoXa3PY
http://www.youtube.com/watch?v=_LoDPNNRbG0
My overflows are 1' at the intake but open into 1.5" outside the tank.
I'm using a Reeflo Dart pump.
Things I did and wouldn't do again:
1) I didn't use a complete coast-to-coast overflow. If I were to do it again using the Dart I would have expanded it across the entire back of the tank. The siphon is VERY strong and if a fish gets pulled in, it basically breaks the fish. I lost two fish that I thought were too "large" but the siphon just yanks them in.
2) I wouldn't use a Dart. In fact, I would just use a 600 gph return and add additional flow somewhere else (e.g. closed-loop, powerheads, etc.). Since the general consensus seems to be "match return flow to skimmer flow" I wonder if Beananimal is a little overkill and if more traditional overflow systems are just as suitable.
3) I expanded the intake from 1" to 1.5" outside the tank. Next time I would just use 1" all the way through, and I would put a gate valve at the bottom of the siphon pipe.
4) I used PVC for the pipes outside the tank. Next time I would use flexible pipe like vinyl.
5) The drop from where water enters the pipe to where it hit the sump is only about 3-4 feet. This doesn't allow the siphon to kick in very well, especially since the pipe outside the tank is 1.5" (meaning it has more air to push out).
6) Once a snail gets into the OF, the 1" is so narrow, it causes the Emergency to kick in so protect things from getting in. What I ended up doing was cutting GutterGuard into small lengths and wrapping it around the intake to keep things out. I added a pic. The only problem was that algae likes to grow on this but this isn't a problem if your tank is well maintained.
The Beananimal OF system with a big return pump is a deathtrap to fishes and other non-squishy critters in the tank so you need to protect things from getting in; seriously. Mine is pushing, nominally, 3500 gph though a 1" hole and that's a lot of flow. Even if you scaled it back to a more realistic 2500 gph, that's still a lot of flow. On the plus side, I'm pushing 2500 gph through a 1" hole and it's absolutely silent!
HTH.