I have almost exactly the same setup and it's working very well. I have 3 or 4 23W cold white (6500K) and one warm white (2700k) per plant. I run 18/6.
Here is my C99 vegging. She is has nice tight nodes and is growing really well. I plan to top her today. Half the lamp is turned off since the other C99 is convalescing from 'claw leaf'.
I do keep the lights about 1" above the plant. Seems CFLs wont burn unless the plant touches them (which happens too easily at 1"

)
Separate veg & flower cabs make your setup a lot more flexible and efficient. I plant to set up a staggered grow and harvest a plant or two every few weeks.