Between 0.5g and 0.8g per watt.
That's the average most people try to achieve.
I don't SCROG myself but have alot of knowledge on the subject as I was going to go down that road myself at one stage.
I personally grow 4 plants under 400w. My last harvest was 427g dry and time before that 439g dry. So I'm up around 1.06-1.09gpw.
In all honesty though you could do 2 screens. One per light with a 1.1x1.1m screen for each light.
That alone will see you up your total again.
I always tell people to aim for 0.5g per watt used and anything more is a bonus.
If you don't achieve 600g dry then you need to rethink your screen size.
J