actually your right about both spectrums being best for flower but both spectrums in the same output valocity in other words using a mh and a hps would be optiomal using mh for flowering isnt unheard off as mand has said(hello temptress) BUT for flowering purposes hps's and cfls would make much more sense then mh and cfls..if its not to late maybe you should look into a switchable ballest which can be used in conjuction with either mh or hps bulbs...