The lumen count doesn't increase with additional lights...
The thing is though,
Lumens GREATLY diminish as the distance from the light increases. If you have one light in the middle, you will need to raise it quite a bit above the canopy to get coverage of the entire area or use a light mover as growtech stated.
Now, what I've never really understood is how you would determine how the
intermittent light from a 1000 on a light mover would compare to the same total usable
full-time light from 2 stationary 600s. There has to be an effect of the intensity of light fluctuating, right? As opposed to always hitting it full strength?
To me,
Penetration would describe depth penetration: how far into the canopy the light will reach.
Coverage would describe the area that the light would reach on a plane.
And even with SOG/lolly, it appears to me that depth penetration is still very important, up until a point of diminishing returns (light wasted right through the bottom of the canopy).
you could get 1 Metal Halide 600W and the other 600W could be a high pressure sodium, using both simultaneously is ideal for trying to get large yields
If you didn't have them on a light mover, you would have uneven coverage. One side would be getting more red light, the other more blue light. I suppose that with the "dual spectrum" hoods, the lamps are probably close enough to minimize this issue, but with 2 seperate hoods, it would be expressed.