Scrog question

When I scrog, should I top the plants before I put them into to flower? because i'm planning on a 2 month veg... this is my first scrog
so advice is welcome, what's the best way to do scrogs? how far should I put up the screen. i'm working with a 4x2 grow tent with a 400 watt hps with two plants.

Not sure if you have read this, https://www.rollitup.org/general-marijuana-growing/438789-lbhs-scrog-tutorial.html , but it is a good read.
I am going to be topping my ladies for more bud sites and to keep my sativas bushier so they dont grow too tall.
My grower friend said he's topped 4 times to create 16 tops, I think I'll do mine maybe twice or so. With scrog, as long as your screen is about 55-75% full before you go 12/12 you should be fine.