I also made a Hofer - it's only been installed for a few days. I still have some tweaking to do as my flow has recently increased, but it's working pretty well and was easy to build.
Here's the link for the build:
http://home.everestkc.net/jrobertson...struction.html
Re: the inner box - I have mine where the water is about halfway up the teeth. Just so you know, the height of the skimmer (inside) box will effect the water level of the tank.