yup, those 42 watters would be good. Dont mess around with 20, 23, 26 watt lights, get 30 watts and up. They'll get a bit hotter, but get a good fan to cool the lights and another to bring in cool air to the chamber. This method of growing, where the seedling is put into 12 and 12 sounded strange to me at first..... and it still does. The plant can't physically flower right away, grow them to about 6 inches or something @18 hours. Like buddy just mentioned smaller plants need less light, so it's a good idea to keep em small.
Have you started anything yet, where's photos?