When I did it I actually just set it on the ground the screen unrolled it and had it laid completely out use 2x4s and you can adjust it if you need to put up a post put in at 16 inches and put one at 36 inches really just depends how tall you want it to get
I top my plants halfway between the medium and screen height. Then weave. I clean under the screen and yeah this creates better airflow. I would have the screens around 900mm high. Make sure you plant them far apart enough so that they don’t overlap too much.
I’ve been doing scrogs outdoors. 2 plants in a 5’x10’ Scrog.
I top twice, pull the plant to one side a bit, place the net about 1 meter above the deck, (I grow on a 3rd story deck), then bend and weave as she grows.
Last year I used some cheap trellis netting, it sucked.
This year I’m actually not growing Scrog. I was hit hard by bud rot and I think the dense canopy helped create the boytritis friendly environment. This year I’ll just top once or twice, do some lst, and let them grow normally.