What intensity you running those at?He should lower intensity, not remove lights. Two lights at lower intensity are much better than one at higher - because you get multi-directional light, and not nearly as many issues with shading inside colonies. This is why pretty much every lighting manufacturer (except kessil) keeps moving towards wider spacing of diodes. (and why big halide reflectors are better)
I currently run 4 gen3/4 XR15s over a 24" cube. It works great. Much better than when I was running a single XR30