Scrogs are all about low even canopy for light coverage and air flow, not height. I would set up the screen roughly 12-14 inches above your pot and train the plant to stay at that height. This will leave space under the screen for air flow, but it will also maximize your height to surface area and allow the least amount of veg time. If you flower when the screen is roughly 75-80% covered you still will want to tuck branches for the first 1-2 weeks of flowering while the plant is stretching. This will give you a nice full screen of budsites. Thats what its about growing bud sites not branches. You also want to use a sturdy screen to grow into. If your screen is sturdy it will keep the plant in place, if it is not then the plant will push the screen around and it will only act as support not really the training that a scrog is normally. I just searched around to find an amazing old thread on here about this, but sadly all the pictures were gone. There was a grower on here named Natmoon back in the day that did amazing scrog grows.