those 4' shoplights are, in fact, compact flurescents. the difference is in intensity. a 23W CFL bulb will emit its lumens in a very small area, whereas the shoplights will disperse them in a wider range. just do the math. 4' @ 40 watts = 10 watts per foot of shoplight. very weak. 23 W CFL = 23W in one area. in the total space required to fit one shoplight, you can squeeze in half a dozen CFL's. i use a combination of shoplight tubes and cfl bulbs for vegging and mothers, but upgrade to HPS in flower. i dont have enough experience to tell you if it works, or if going straight cfl all the way works either. sorry. but 6 x 40W = 240W CFL. not bad, i'd say, but very few growers use less than a 400W hps, which emits more lumens than 400W cfl's. and you have roughly half that :/ doesn't sound promising. if the math is indicative, you can expect less than half the yield you would get under a 400W hps, and a fraction of what you'd expect under a 1000W Hps.