So that is 18in tall correct? Does it have the dome light screen on it? I opted out of those on mine so I mounted a fixture inside the cage. I have some 322's so those are 21in tall. My fixture inside drops the bulb surface about 5 inches down. With that being said I use a 35W Par 30 Flood bulb in those cages and don't have to regulate, my ambients are close to yours, but drop at night...