I did them up higher as the tank was sps dominant and most of the sps were up higher and wanted more flow hitting them then if the tunzes were lower. Either would work fine. The tops were open and the water would go all the way to the top when turning on and off. I still got the wave action in a four foot tank with this design. The original plan was that I wanted everything out of site and figured this was the best way to do it. Incidentally I had hoped they would work as wave box's and they did just that.
Spazz could do these on custom tank builds with the cnc. These were were hand made and can't imagine what a pain it was to cut the slots individually.