Hey brother and good luck with your upcoming run.
32" isnt too small for a screen. Remember that the idea of the screen is to have an even canopy so that all the buds get (somewhat of an) even intensity of light (vs top buds getting good amount of light and lower buds being too far away from the light source). Also, the screen helps greatly when it comes to hight limitations (man some of these strains double to tripple or even quad in height after flipping the light).
You dont have to set the screen 7" above the growing medium. Many prefer to set their screen 12 inches above it and I set mine about 18 inches above the medium to allow for mire room to work underneath the screen.
Now, as far as filling the screen goes, what you want to do is allow the shoots to grow horizontally under the screen. When the shoot goes above the screen and grows like 3-5 inches, you can bring it back below the screen and move it farther away and into the next square.
You dont want to fill the screen completely and you want it only about 75% full before you flip (less full (like 60%) before the flip if you have a stretchy strain or a sativa dominant girl who's going to stretch)
You can check out my current and previous runs where I scrog 3 and now 4 different plants.
Its actually easier done than said
Check out my new QuadStrain grow

:
https://www.rollitup.org/index.php?threads/916619/
and my previous TriStrain grow

:
https://www.rollitup.org/index.php?threads/883569/