There's all sorts of theories on when and why plants grow bigger. The thing is, going to a 12/12 light/dark schedule tells the plant that it's time to reproduce, and it grows flowers. I'd be very careful of going to any sort of equal light/dark rotation until you want the plant...going back and forth with that stresses the plant in a way that more likely to give you a hermie.

Btw, depending on your placement and reflectors, two 40 watt cfl's are enough for one plant. It's about lumens, not watts. (Watts = energy used to make light, not the light itself.) Two 40 watt cfl put out around 5300 lumens...that's enough for about a 1.2 square foot grow to do ok. 2000 to 2300 lumens per sq. ft. is a minimum; 4000 plus is much better. The thing is, most people don't use the lumens they have. Keep your lights close and get reflectors and your plant will grow better and you won't need to add light, which will cut down on your heat, stress, and ventilation issues.

Also...if your plant was 10" and grew another 3-4", you're definitely in the area where you want to think about flowering. I don't know how much space you have, but that plant is going to grow plenty more during flowering.