Lowering light

you'll get better penetration from more variety of angles with greater height... but also more loss to the walls or missing the plant too. Getting it closer only reduces the angles at which light hits the plants. more direct paths with less bouncing off walls at at more acute angles... better to be a little wasteful but at some point there's no benefit to doing so. i'd stick to a height that provides the best overall blanket of intensity across entire canopy. Especially if oyu use QB. those don't take advanage of diode size for distribution of light... bunch it all up for no reason other than a lack of imagination in product design that doesn't utilize the best qualities of the mid power chips.