but what I am wondering is at what size or how many days will they have to be under the CFLs before we can throw on the HPS.
You can veg. cycle as long as you want too, under the CFL's, but most growers veg for 30+ days, 12-15 inch tall plants. The light cycle will be 18/6 or 24/0, growers choice. Then you start the 12/12 flowering cycle (check indoor lighting forum, about CFL's or Floro tubes))

The ceiling is I think 6'8", so there is about 4 to 4.5 feet from the top of the grow tub to the ceiling
Your're not gonna have much space left, after you hang a 1K light. And the 1K light will have to be at least 20 inches from top of the plants, maybe more. This is the space you HAVE to keep at 75-85 degrees.

Hi Skrappie...I'm really not very good at advice. I'm a master smoker, not master grower, but I try to help out here and there...imp: