^^This
But... or you could just do it how I do it, have 8 plants per 600w, veg, a short finishing High yielding stocky indica, for 5-6 weeks, and grow 75 grams, AKA just over 2.5 OZ a plant, if you have a hard time believing there is 2.5 OZ a plant in that picture, then I guess you just have never seen a 2.5 oz plant?
Sorry if you cant, hit a gpw, truly I am, but that doesn't mean it isn't FAIRLY easy for others, myself included, to accomplish.
Plant numbers, plus correct training/pruning, plus 600w lamps with the right amount of space, A GOOD NUTRIENT with a dialed in feeding regime used in a form of PURE hydro, the correct genetics, along side a dialed in environment (genetic specific), and a completely happy life for the plant (from clone to harvest) = a gpw there is no argument about it, it gets accomplished by many people every day, if you are not not hitting it, you simply are not fulfilling ALL of these requirements, and that is a FACT, PS notice I said 600w lamps, I do not hit a gpw with 1k's, more like .85, perhaps I could if I used a lot more space per lamp, either way 600w vs 1kw, make a big difference when it comes to 1gpw for me, YMMV, good luck
Nice work Green_science! Do you have an approximate on amount of space per 600w?