Keep that light as close to the top of the plant as you possibly can. Just make sure the temp at the top of the plant doesn't go above 80°F. If you have a sealed, air-cooled reflector, you should be able to bring that light within 2-3" of the top. If you don't have that, you will probably have to keep the light about 10"-12" from the top. The point is, the closer you can get that light to the top of the plant, the bigger your yield will be because you'll be giving your plant a higher concentration of light output. Also, when harvesting, don't be afraid to harvest the plant in sections based on when individual buds are finished. By doing this, you will give the smaller buds towards the bottom of the plant more time to pack on weight once the larger top buds are removed. Finally, I recommend you look into a product called "Gravity" by Emerald Triangle. It is a flower hardener that will increase the size and mass of your buds. Just be careful not to use too much Gravity, and make sure you reduce your nutrient solution down to 1/3 strength when you are using it. Gravity causes the cells responsible for photosynthesis to become extremely sensitive, almost "supercharged", so you also need to raise your light by about 10" from where you normally keep it. First and foremost though, you should decide on an appropriate nutrient combination to use during the flowering phase. You want to squeeze the most bud possible out of this, and making the right nutrient choice is of paramount importance.