strain, and veg cycle play a role in overall height. Indica, short and squat. Sativa tall and branchy. I have read that cfl'c will not support a plant over 20 inches in height very well. It would require to many of them. IMO if you have 8 42watters you may as well buy a 150hps and get more lumens and probally less heat. I know cfl's run cool, but you get enough of them and you will notice heat