I would place the light a few inches off the floor (in an open space) then raise it slowly to see how well it covers. Most hoods are not square in their reflective pattern. The placement of the bulb and if it has a second reflector can make a difference. Air-cooled hoods are different then non air-cooled hoods too. Learn the difference in your hood and place it that way. You want the best out of the light for your plants. Try that or use a light meter.