Downsizing

Hey,

I currently have a grow room 4ft wide, 7ft long, 2x 600watt HPS.

My last crop yielded me 50 ounces (8 plants)
This time I'm doing 6.

I need to downsize just because it takes up too much room.
I'm going to buy a small grow tent maybe 3ft length and width. (After this crop)

I was wondering if anyone has grown 4 plants under a 600 HPS or even a 400
and what sort of yields you had.

Thanks.