technically, any green surface of the plant can use light for photosynthessis, but it is extremely attenuated on stems and underside of leaves -- lower density of chlorophyl existing in those surfaces and not as close to the surface as the top of leaves -- you can google this to verify... incontrovertible truth. So, any watts of light pointing at underside of leaves is less efficeint in a large way... some side lighting that 'can' hit tops of leaves and provide more radiation to previously shaded areas will help growth in those areas, sure. The reason why outside plants can get so large and consistent buds all over is becaus it is swimming in light and inundated by it from all angles. So, if oyu mimic this and try to focuse more on top of leaves, you will definitely imprve the buds in these areas, in similar fasion as to why plants grow so much better outside - far less larf underneath and only in the most shielded areas. If you have a good baseline for normal yield and using plants you can count on in that respect, you can compare your experiment with those baseline results and make an informed decisions if the extra watts spent justify the increase in yield... this is really difficult to know from a small sample size... using clones and a very tightly controlled environment may still need a large sample size... more variations just make it less certain that the change you see is caused by the extra light.