Raybo I have been using the the same setup for about 3 years now and have had good success. I agree 1 per flat is not enough I line them up and space them as needed I have about 10 now but not sure how many will be in use this year due to the upcoming adoption I will not be starting as may this year. Here is a link to my setup from years past for anyone that is interested. I had a couple of the older T12 lights in this post but now have all T5 lights.
http://www.tomatoville.com/showthrea...ghlight=gobigs
Craig