I have a 2 x 4 and watering isn't much hassle. If I was gonna try it in a 4 x 4, I would do 6 plants topped twice and flipped after 35 from seed. I would set the pots in a row about a foot and a half in. Remove the larf and suckers before you put the trellis on.
The way I do it is veg without the trellis put the trellis on when I flip and start bending. By time they quit stretch, the trellis is full. These two were 30 day from sprout to flip.