i have grown 2 times in 3 gallon buckets at 12 12 from seed. i know about how tall (give or take a few inches) every plant i grow will be. in my 3 gallon buckets they never get more then a foot and a half tall. just started a 32 oz. cup grow to try and maximize yeild with my lighting. i want atleast 8 plants under a 250w hps, and 125w full spectrum CFL. but anyway the size of your plant is relative to pot size. you can grow a 5 to 6 ft. plant in 3 gal. pots, but you have to veg. for a month and a half before switching. if i had your exact set up, i would try and take advantage of all that light, and either LST like the other guy recommended, or grow in smaller pots. FYI do not veg. 24/0 do 18/6.