Have you thought about using reflector walls around the grow beds?
Right now I'm using white 1/2" Styrofoam sheets I've read they are 85% reflective. Mylar film takes you up to 97%. For some weird reason I don't understand aluminum foil is the same refractivity as white and flat white works better than gloss.
Mylar is not cheap on rolls but, Space Blackets are cheap and they are made of Maylar. My next MOD will be to wrap my panels with a space blanket. In a bigger system like yours you could simply hang them like shower curtains.