Hey dude,
My experience with a SCRoG is limited to 0. Nada. Zip. Zilch.
But anyways, here are my thoughts:
1. With SoG or SCRoG, you train your plants constantly. I don't think it has to be 3" above the screen to start bending. Just, as soon as you can "web" your plant and it's branches into the screen, you start with it. Plants are pretty tought mother fuckers. I've LSTed mine, and they end up being completely horizontal... and withing 24 hours, they've grown in a 90degree angle and are pointing upwards. Just do it little by little.
2. I don't know if you want to LST/SoG/SCRoG them so late in their life. When you start SCRoG from the beginning, you end up with many bud site, all at the same height (more or less). The main cola, is actually, one of the crappiest bud nuggets. You bend all the fan leaves below the screen, so only the buds and their leaves receive the precious light.

Not sure about your situation... just my 3 cents.

Best,

-turtle420