shit if ur pulling 81 4" above with 20 lights id say thats pretty fuckin good! whats the distance between the top of screen and the highest point u can get lights? cus your gna wanna have lights mounted directly to top of box once u hit about 3 weeks into flower or u wont be able to move lights after that.. cause you wont be able to do much inthere except train them and water them at that point.. i wld highly suggest a small water pump and hose to water with.. rather than syphoning like i did.. not very fun lol