Not bothered either way mate. I thought to myself earlier that she's probably a 45 year old bloke called bill. You can be anyone you like on the internet.
You might want to lower the veg time down to about four weeks if you've only got 6ft of height. You would probably want to flip them once they get to about 2 ft high.
I haven't any experience with vertical growing but either way if i can get a 400 10 inches or less from my plants then I don't see why 3 ft with a 600 shouldn't be ample with the fan in place.
Cfl's don't need a ballast mate. At the end of the day why would you want to swap down from a 600? 600 means more bud. Also I have grown out a little lowryder no 2. Nice little plant it was but I only pulled about a q of it.