On my most recent grow, I used a layer of light warrior on the bottom of the pot, then the 70/30 mix, with a 1 inch layer of hydroton on top of that.
The hydroton lets roots take up as much of the pot as possible, instead of stopping 3-4 inches before the surface of the soil. When you water, the soil underneath the hydroton does not get disturbed or compacted (a problem I have experienced when using FF OF).
The light warrior ensures the roots get plenty of oxygen.