its quite pointless to line the bottom with egg crate. the glass base is re enforced for the weight of heavy objects and egg crate actually makes it harder to stack rocks.
Well, Im hoping my aquascaping skills are up to par. None of the rocks in my 37G FOWLR tank have fallen thus far, even though my fish dig out the substrate from under it!
If the rock is stood on the base of the tank, the sand in a dsb could help to stabilise the base of the rock. However if you stand the rock on top of the dsb then burrowing fish are more likely to burrow under the rock and get crushed. Depends how you set it up.