I always use the COB's first . I use the pray & lay method. Raise the light about 24-30 inches watch the plants and see if the leaves turn up (pray). Lower the light if they do (2-4) inches. Watch the plants for a day. If they still pray continue lowering until the leaves lay. Once they lay measure that distance to the top of the canopy. Raise the light till they pray. Measure again and maintain that height. Once the plant get hardened you can run the light lower. After a couple of weeks of growth I will turn on the "mono's .