The tanks cascade right now but when I move in a few months I'm planning on re-plumbing them both to the sump, adding a second return pump, and return mainfolds with scwds. http://www.wetwebmedia.com/pbh2oret.htm.
I had to add a valve on the nozzel into the lower tank to eliminate the bubbles (you can see it in the pictures of the 50gallon). Here's a link to the original plans, some things have changed, but its still pretty close to the way things are. http://reefs.org/phpBB2/viewtopic.php?t=34501&highlight=
very nice setup gabe! i would never have thought that you can put another big tank on a smaller tank because of the weight. i like it, gives you two looks in one area