That looks really nice. I was in HomeDepot last month staring at the aluminum stock thinking the exact same idea and bought a piece to experiment with that ended up as a reinforcing bar on my current light mount you can see in my photo. In the end I though better of it because my tank was too deep front to back and I wasn't sure if the aluminum would sag with a 20 inch or so span. That and not knowing just where I wanted position the lights to begin with having an oddball 36" square area to light I decided to go with the LCD arm etc.