I use the same exact ones. In my 4.5' x 4' room I use 2 of the 4 footers along with the nano reflectors. I will tell you right now....DO NOT UNDERESTIMATE these lights. The first time I used them I worked on my plants with one of them overhead for about 15 minutes. That was a HUGE mistake. I have pictures of the blistering on the sides of my face and neck! It was horrible.
I learned quickly after running them a few hours at a time 3 times durring each lights on that that was way to much and burned my plants up.
Over time I have found that having them about 2 feet away from canopy and on a timer so with every 12 hour lights on they come on for 15 minutes about 3 hours into lights on. After 15 minutes they go off for 1.5- 2 hours and on another 15 minutes. They turn on 4-5 times for each lights on period but I keep 3 hours on each side of the day with them off.
That works really well and 2 of them cover my room FULLY and never need moved. I will spin my plants around every few days though.
These Pure UV bulbs are crazy. With the reptile bulbs some people use I never came close to the power of these.