Got one of them Photone apps recently. Realised the tops directly under my 600w hps were frying at like 1800 ppfd! No wonder they were always foxtailing and just getting huge and ugly lol. Now I just try and control the canopy so that directly below the lights I have the plants tied down much more than the rest creating a more light even canopy.
Still have em frying at around 1200 in the middle and around 600 ~ 900 around the sides