Cloud walker (ScroG)

you've got about 45watts per sq ft. If this is a high efficacy light, you only need about 32-33w per sq ft. 75% is probably all you'll be able to do... definitely observe plant and react to how it behaves. this is for a mature plant, not seedlings. But you can always use resulting internode length to guide adjustments. too lanky, needs more. too tight, needs less. This can be a good thing. you could also run with a little extra waste of watts, raise light slgihtly, if possible, and get a more even distribution across canopy. Is the yield boost going to justify teh extra watts? no idea. but, you will improve quality of buds along edges and corners. using a phone app you can adjust power so that you get that same value in center, and should have an improved value on edges than before. Sometimes a tent or grow space doesn't allow an extra 2-4" of height, so it depends on your context there. It won't take much extra distance to improve the outskirts and there's a point where it definitely becomes too wasteful or a detriment to larger central area under the light. So, as far as distance, i'd pick this based on distribution of coverage across canopy -- and assumes it causes no damage to anything, of course. even 2-3-4 weeks of exposure. small problems takea long time to progress. take notes. fine adjustments require more than "feel"