cash4hash,

i am growing with a 400W HPS and my seedling started about 24" away from the light and i saw great growth despite the distance. it has since grown and is now only about 12" from the light and its starting to get to the point where i may have to raise the light. What I would recomend (if you are still taking suggestions) is to leave your young seedling a good distance away (at least 18-24") from the light b/c while young it is suceptable to being burned if too close. It will still grow just as well (at least mine did). Then, if you really want to get it as close as possible, I would lower the light to 12" from the top once you have at least the 2nd-3rd set of leaves. You really dont need to, as i have seen in my grow, but i think the closest it should be is 12" and the furthest 24".

Hopes that advice helps.

-JPG