I'm running a coast to coast or "Calfo/Herbie" on my 120. It's similar to the one in the post above but I only used a single siphon (downturned elbow) and a single emergency (upturned elbow). To regulate flow I have a valve between the siphon and sump. Has worked perfectly and is silent once the level in the overflow is adjusted with the valve. The emergency drops straight down to the sump and stops about 2" above the water level so you can hear running water if it's working. I've only had to rely on the emergency once (plugged the siphon with a bag while acclimating a coral) and it handled all the flow. Here's a pic that shows the emergency side:
I went with this design after visiting a few LFS's and noticed a film floating on some tanks equiped with just a corner overflow. I also liked the idea of only drilling the tank at the top rear as the pressure is significantly lower than near or through the bottom. Plus it was cheap! Just the plumbing and two pieces of glass
