5 gallon pots for 2' plants? I wouldn't go with anything bigger than 3 gallon, unless you're are topping and pruning to keep them at 2 ft (longer veg time - more time for roots to grow) but if your just going to flower after they reach 2 ft, you have 2 -3 gallons of wasted space in your containers. Do three gallon pots and then you'll be able to utilize your grow room space and have more plants. I use 2 gal. pots for 2' ft plants which work very well. The general rule is have 1 gallon of container space for every foot of growth.