I have been attempting to "sort the wheat from the chaff" on this one for a while. I've got 400w of veg bulb and (in total) about 450w of flower bulb for my plants utilising a properly appointed 3m high growbox approx. 0.5m sq (small I know). Can anyone out there with some experience let me in to what must be a bit of a growing secret (a friends bad advice may have just cost me the sex of at least three plants)? Is it the heat from HPS that makes the diff? Should I keep my frost protectors on daytime to boost heat (walls are matt not Mylar)? Combination growing has been suggested (one veg bulb one flower) but When I tried combining the two (for just a couple of hours one morning having switched one bulb back to veg the night before) they finished sexing (yeah, that was stupid) in two hours and left me with four plants only one of which is now recognisably female, however the "Soft Secrets" article he read suggested spectrum combi lighting would be better, what gives? I quoted the guy who grew his AK47 under flouros only (and showed his pics) on another site, does anyone know who it was?