When do you attach the plant to the screen in V-SCROG?

I'm am thinking about doing a vertical SCROG with a couple of 1k watt bulbs in the middle, and eight screens, forming an octagon of eight plants around the lights. The number 8 is the legal limit for my wife and I, not a tribute to Chuck Norris (hopefully the weed will kick my ass like Norris would).

Anyway, at what point/at what height do you start training the plant to get on the screen?

This method just makes so much sense to me, especially if I am going to be vegging out a limited number of stretchy sativas.

with 8 plants you could get away with 1x 1000w light i reckon, maybe top the sativas to keep them 4-5 ft?
I kinda like the idea that you put the screen behind the plants/on the wall, then just tie the branches back that grow too close to the light, so they cant get any closer.
Seems easier than weaving through.

How about 1 2,000w HPS

Go with 2 lights and let the girls stretch. 2 lights stacked will net you far more and you won't have room with 8 plants that are all sativas if you top them IMO (I am doing something similar at the moment). If you go with 2 lights and just let them go tree style with some training your bottoms will be almost as nice as your tops. I currently have 7 plants, 4 corners have large sativas, and I could have room for 1 more in the tent but it would be a tight fit. As it is it's a tight fit. If I had topped anything it would have been a giant mess to train and keep the canopy even and the plants receiving similar light.

Given you might want to go perpetual I might suggest going 4 plants with training grown tall while your other 4 veg out, you can work a cycle out to get it going perpetually I'm sure.

Good luck, vertical is definitely the way to go!