The trick for me was to find the right types of strains for my particular environment, along with the the optimum veg time prior to flip.
Plus, I've always had better yields and less hassle growing the same or similar strain for each run. With the right strain there is no reason you can't achieve 1oz per plant, when you dial it in, you'll get closer to 1.5 per plant, maybe even more.
I use a 4 level 72 site 2 gal hempy in 100% perlite with 2000k. The major breakthroughs for me were, #1 switching from soil to 100% perlite, #2 vegging to about 16" and, #3 keeping my temp range between 76-80 degrees. The lower temps during flowering really made a difference in the density of the buds.