The center of the bulb is the meat. You get less light "lumens" coming from the tip than u do the base. The light is stronger in the middle, less from the tip and more from the base. Hang it from the base. Once u have the bulb surrounded put the base height around the top of the plants or a little lower. From there small adjustments up or down can be done by shielding your ojos and observing the light penetration on your plants. In about 5 seconds you'll see what bulb height looks the best. Turn your plants every day. I start introducing the small fry to vertical lights early in veg and wean them off overhead weeks before flipping them. Don't fret over the odd fans that result from vertical growing. Some get big and long, measure 12" or more...don't cut these! This bullshit of oh their covering bud sights let's cut them off! Ugh those fans are supplying the energy to grow and feed those buds and everything attached to them...during flowering. Weeks 4-5-6 can be daunting staring at a vast area of green fan leaves but endeavor to persevere. go stripping the plants of fans and make the plants rely on small leaved bud surface area to take up the energy production and you've just handicapped your plants. Realize the light is shining through to the back of the plants opposite the light, by turning once a day every thing gets its share of light..even the buds. Plants without fans make for great photography but what could have been if you'd just set down the scissors worrying about bud sights. So vertical can be as simple as turning the plants every day and not having to immobilize the whole thing to a cage.
figured this shit out back in Feb. An old thread brought back to life.