"DIY COB$, Double Your HID Footprint and same/more PPFD for same KWH"
I learned this from reading @SupraSPL , @Growmau5 , and other bright fellows' posts here at RIU and elsewhere...
For a typical (1) 1000 watt HID (HPS/MH), you can double your footprint (from 4'x4' to 4'x8') for the same KWH...