I did last summer. I filled 5 gallon smart pots half way and the rest with base soil. I even put a one gallon smart pot on top of that just to be safe. Unfortunately all of my plants were stunted. Not because of the SS, but I think my water is too clean over here (recently moved to another country). But I can say that the plants that did hit the soil, startedt to grow nicely. Oh,and it was DANK. I just wish grew bigger. So this year, I mixed my old super soil with my old base, im using this as my base. And I re-amendend the super soil for the bottom layer. But go for it!! if your going to with just the 5 gallon, 1/3 shouldn't hurt anything. Try googling "autoflower TLO Soil" Somebody on Autoflower. net grew in a hot soil as well. pretty good yield.