Myself, I use flo's until thier over the sprout period. 2 inches above the plant. When ya go to the MH for 5 wks, I keep them at about 2-2.5 ft (1-400w) Veg time I add on 3-400w HPS and keep em at about the same distance. The room is covered in mylar.....walls, ceiling, floor...

Thats just my method....I'm sure that there's a lot of different success stories out there with a different methods.