There are also a few options with Herbie style overflows, I personally prefer to use a standpipe as the secondary drain as appose to a straight pipe. This will allow a little more freedom in adjustment and give more tolerance meaning you won't have to adjust the valve as often to keep the system quite. Here's a diagram I made a while ago to illustrate this:
I would suggest you don't tee the two drains together at the sump as shown though, keep them separate for best results. You can also use a stock-man style standpipe rather than an HGB.
HTH