If you have the old high bay HID fixtures that you are looking to replace take a look at the 6 lamp T8 4 foot Watt Hawk fluorescent high bay lighting fixture. It has a 95% specular reflector that produces an even lighting pattern that eliminates shadows and hot spots. This fixture is so easy to install that most businesses can install them with their own personnel if they need to.
Take a look A 6 lamp T8 8 foot fluorescent high bay lighting fixture for your lower mounting heights. It is recommend for mounting heights of less than 15 feet. It will throw the light within towards the side within 3 inches of its horizontal mounting area. It will spread light side to side quicker than any other fixture in the industry. With the aircraft hanging cable and different cord sets you can mount it yourself.
What a way to easily replace Low Bay fixtures and increase your lighting coverage as well as reducing your wattage consumption.