A high yeild of well past a gram per watt seemed unbelievable to me also , i grew over 20 yrs & couldnt bust a gram per watt , now anything under 1.25 g per watt means somethings off or my clones werent up to par .
It took me over a year learning from Albfuct to understand why & how but its all in the clones , you must have large clones with multiple nodes , preferably 6 or more nodes & no branches , all nodes must be closely grouped on a single branch , using veg time to make up for unsuitable clones actually works against you , go to the sticky of Al's ( A Batch of clones ) & look at his choice of clones , you'll see all single branches with multiple tightly packed nodes & NO SIDE BRANCHING, put 50 clones like that in a 4 x 8 & you'll beat any previous yeilds you've had .
Hitting 1.5 g per watt allways sounded like people were lying to me , that is until i put the effort into replicating their methods now 1.5 is a normal thing for me .