Let me elaborate on my earlier statement... You can run these on 4ft centers, 5ft centers even a 5x6 or 6x6...
If you have plenty of sq footage but electrical restraints run them further apart. Some of the colas might be slightly smaller on the outskirts but it will equate to more weight. If you are maxing out your electrical and run out of square footage then run them closer together. Gavita has made us light plans both ways depending on our specific space.
Long story short, you can run them between 4x4 and 6x6 and anywhere in between. Just my 2c