Best vertical light configuration???

I'm getting ready to add a 600w hps to my current 400w and they're going to be in cooltubes, set up in an inline vertical configuration from floor to ceiling. My grow is in 5gal dwc buckets, surrounding the light. I'm torn about the best way to configure the lights and would love some feedback. Btw, i have 3 females in there vegging for 6 wks right now, and i'll be adding 3-4 clones next wk that'll be thrown in there right into flower(no veg time), so there will be 3 plants that are tall, and 3 or 4 that are much shorter. What would be the best use of lighting for my situation.(ie 400 on bottom with socket facing down and 600 on top with socket facing up?) I can also even out the canopy a lil better by placing the clones on blocks if need be. Please, any help would be greatly appreciated! I've been racking my brain for the last few days bout this. :upsidedow