Keep it at 24/0 or 18.6. DO NOT GO TO 12/12 or your plant will go into bloom from seed and it will be very small. With 11 seeds, i assume you got enough space to get bigger.
A plant will typically double in size during flowering.
CFLs are most effective when they are close enough to shroud an entire plant. (within 1-3 inches)
Therefore, you want to flower at a point where it will get big, but small enough to still be effectively grown with CFLs.
I am starting 3 seedlings in my closet right now and I plan to flower at about 2 weeks.
How many CFLs do you have? And how much space?
There's a lot of information on this site. Do some research!