Thanks for sharing! Are you talking about dry weight or wet weight? I always reference to final dry weight.. i am seriously amaze if youre getting 2 pounds with a 600w hps.. simply put 400w of more efficient light will get you the same result but 2 pounds off 400w LED that sounds very surprising.. are you using co2 ?
650-700w should get you about 1000ppfd accross the canopy.. with co2 you can go up to 1500ppfd I think.. im not too savy about co2- and also I wouldnt recommend for your first grow but added co2 in good set up should yield you an additional 20-30% if done correctly