Bend over, tie down, get the light real close to prevent stretch, and make sure you're using blue enough light. Intense blue light such as from a MH= less stretch compared to the red light of a HPS. Of course, you still need that range in flower but with a big sat, every little thing you can to to control height helps! Also, keep your temps from fluctuating between night and day if you can. It's not critical, but is also a factor that can help reduce stretch.