This is true, most likely your artificial lighting is not going to be intense enough at the lower branches leaving you some wispy crap down there even w/ a 1000w. You want to stay short enough so that your light is still pretty intense even on the lower branches. You can supplement w/ side lighting if you have to. Which I am guessing you will.What kind of light are you using?
Even if you are using 1000 watt HPS ,you should be flowering right now.