yeh the only thing that matters if your factoring in plant size, is how often your gonna water no matter how much water you give it each feeding. 1 full gallon of water for a 5 gallon bag is just fine, and youll water it more than likely every 3-4 days. My plants are pretty thirsty, 2 days after each watering they get a little growth spurt in them, which means that theyre searching for more moisture in the bag, and stretching their roots out to find it. I give it two more days beyond the spurt to dry out the soil. This has happened every single time i water without exception, and itll continue to happen through flowering, only the buds will swell rather than the plant get taller and bushier. I use 3 full gallons of soil, and i only feed my plants about 3/5 of a gallon every time, and i still need 4 solid days between waterings.