Gary Majchrzak
Team RC
placing eggcrate/light diffuser in a DSB is one of the worst choices one could make IMO/IME. It's also my experience that light diffuser doen't leach PO4 and I have yet to see anyone prove it does.I've heard that people use eggcrate in the DSB then fix the rocks on top but I know eggcrate can leach phosphates so you'd want to coat it in something reef safe before if you decide that route.
You don't need to place feet on rock.
You should stack rock so that there's a minimum of contact between glass and rock. This is to ensure good circulation all around the rock.