Over the winter I installed 16 (four rows of four) IBZ 454 lithonia T5 54W high output fixtures in my 40 x 60 x 12 shop. Concrete floor, OSB walls painted white and white metal ceiling (roof style panels). I am thrilled. I used the visual basic software to determine number of fixtures and placement. I purchased them from my local large electrical supply business for 117 each (no bulbs; bought a bunch online). The best part, was realizing the ballast is designed to run two or four bulbs via switching. Charles (in GA) helped me out there - I used the double throw double pole switches he has mentioned previously. I split my lights up so I can walk in one end of the shop and use one to several fixtures in one "region" with only two bulbs per fixture illuminated (all I have needed so far) or all four bulbs per fixture for a very nice bright effect. Suspended about 8" below ceiling per recommendation on back of light. No glare and they don't appear too bright at all, even suspended below a 12 foot ceiling. Well worth my time and money.