Hey man what kinda lights do you have? If its a (HID) then i wouldnt thin it at all. the lights intensity will be able to break through the canapy.But if your doing CFL then you could do some trimming and i would reccamend flowering at 4 weeks because its gonna grow a bunch still and you wont be able to provide as much light as the plant requires. you would have lights hanging all over the place.Dont get me wrong i have done CFL and it will still give you an ok Harvest but when i switched to my 1000w HID Woooooow. The Diffrence it makes is all im gonna say about that. I think my CFL all together wer like 15000 Lumens. Now with my 1000 watt Hortilux HPS HID it like over 100,000 Lumens....