What yield do you pull from a 4x4 ?????

Just above 3 lbs or 52oz with 1200w HPS/MH in DWC. I like to develop a really nice root structure before entering flower. I train and scrog all of my girls.

I most often run 4 plants and I like to veg for a long time. When you have some successful runs and developed some understanding through experience you should look into studying how to use safe PGR's and their role in agriculture.
If want to grow medicinal or you are going to be in any number of situations that require your cannabis to be tested, keep in mind that PGRs are banned. They CAN help you grow more bud..... or they can help your shit foxtail like crazy if you your plants have weaker genetics/you feed too much PGRs/you feed PGR for too long. Like this guy ^ said: STUDY up on Plant Growth Regulators. IF you want to try one, look into "massive" by green planet nutrients. In the "massive" stuff, they derive the PGR from honey bee waste, so its all natural, at least.
Aks @ttystikk if it is possible.
Ask @Renfro
Experienced and well known growers.

You don't have to trust me. I am not saying it is that easy; one should have a dialed in room (or how do you call)
People who use CO2 will easily reach those high numbers.
Which means that the plants can handle it, also in a smaller room.
Just because you don't succeed in it, it doesn't mean it is not possible.
This, right here ^

Just because you dont succeed, it doesnt mean that nobody else can
BlackDog has a video of their 1000 version pulling 2.78lbs from a 4x4 with CO2. The 600 version pulled 1.6lbs in the same parameters. It’s not a bad video, shows some of their defoil techniques:

edit: the nets are 4x4, the space is 4.5x4.5, I confirmed.
Just watched this, not only is it 4.5 x 4.5. The XL 1000 light (the biggest light) only pulled 355 grams.

You got me all excited about finding out some new techniques only to see yield that's poor for industry experts.