I know you didn't ask me, but please, allow me...
With only 4k you shouldn't really run this system, it's not the best use of your resources. Grams per watt will be very low. You should do something like this maybe instead:
[Youtube]http://www.youtube.com/watch?v=3Sa1IIgmtqY[/Youtube]
Or there are many other ways to yield better when you have a small number of lights but this just isn't it. This no longer is really practical or economical and is just an experiment or to play around if you run that few, which if you're going to experiment I'd say whatever you do make sure you have one plant with 4k right where it's supposed to be on it and watch it grow. Any other plants screw them light wise don't arrange the lights away from the center plant for them, they just get what they get in the best way you can manage.
It would probably actually be best to put a ring of small plants around one big one, growing in a different style to keep them so they don't get so big they shade half , maybe scrog them vertically so it's a flat circle around the whole thing then you aren't even growing anything that gets shaded. VSCROG around a tree basically with the whole chiller and recirc and not lacking in water circulation or air and everything else. The outer plants wouldn't need bins necessarily they could be in a ring of 6" pipe or something like that as in other grows if you wanted. That way you could fit more thin plants in a ring of pipe with water circulating and air at ea plant site. Don't ask too much from small air or water pumps if you add more demand than dd's setup like more air stones because of more plant sites add more supply. I know I said that a couple times but it's important to get everything equal or better or you are really really wasting your time.