Hi avrum, from what i have seen 8 heads is most recommended for indoor grows. if you were growing with a 600 or 1000 then going 16 might be ok. i would say do 8 and you should be ok.
quick few pics day 27 of 12/12
1st 2 pics dog no 1
2nd 2 pics dog no2
3rd 2 pics gigabud