room for roots

would i be able to determine sex in a pot this small or would the roots not have enough room? if it helps, im trying to 12/12 when they're about 1' - 1.5' tall.

https://www.rollitup.org/newbie-central/154927-my-planting-tip-16oz-cups.html may help.

these are all females from seed

https://www.rollitup.org/grow-journals/151253-12-12-seed-harvest-1-a.html