For clones, plants I want to stretch (yes, there are times for when stretching is a good thing) and more sensitive plants I keep my 400's about 18" away from the tops and 12-14" for growth and flowering. My 1KW is kept about 3' above the vegging plants and covers about a 4' x 6' area and I do not use 1KW's at all over clones or the more sensitive plants. the 3 400's are in the flower room and cover a swath of about 4' x 10' and will soon be adding one more 400.