So...what did you find out?...I read about the MH bulb being used through flower, and am doing it now, but I am thinking about switching the bulbs every few days to see what that does, I have flowered under the HPS a few times and they just get too darn hot...I haven't had the cash yet to get an air cooled hood, and kinda started making one, ---got the whole thing built and put together, but then hubby lost interest and hasn't yet picked back up to wire the thing...but I have the glass reflector part made---anyway HPS gets too hot and I don't have a way to cool it down---my circulation fan makes it cool enough for the MH, but not the HPS so I started looking it up and found somewhere where someone said that it would make less dense more resinous buds, and then I found one thing that said they noticed no decrease in yield or quality, but that it was somewhat different and more resinous...most people say just to use HPS and stop asking questions...lol. So who knows, but I am using one and am in 2 weeks of flower so far...things look good and the same as the HPS only cooler and decidedly less yellow...lol