ive had 9 plants in a 10 gallon container in dwc....who cares if the roots get tangled(what do you think happens under ground in the earth? do you think the roots just grow straight down? they grow everywhere and get tangled)..doesnt hurt them. and subcool grows two plants in soil in 7 gallon containers and grows them pretty big..so im sure if you flowered right away you could do it in 5 gallons