6- 10 should be fine if they arent to big are u gna do sog style cuz i started flowering with my plants around a foot tall and they grew like 2 ft under a 600whps and a 400 w hps heres sum pics, they are og kush and the short ones are sour diesel they are at the beginning of the 4th week also there is 14 plants all together and thats how they look hope this helps