Scrog question

So I'm about 30% full on my screen but I don't want a lot of over growth above the screen.. should I wait till its 80% full then go to flower 12/12 or about 60% full and fill the screen with the flower stretch...I only have a 400 watt so I don't want it to tall over screen after the stretch...but I don't wanna flower to early and not fill my screen

Keep tucking the tops under the netting this will get the plant to produce more tops then normal,Once the full screen is full then flower if you want you can then put another table over the plants.

Because you have not flowered yet and the plants are at the table top all ready then its a little late for you to holt growth through the table top.

I think it's good to have it switched between 60 and 80% indeed !
You may put pictures of this every week so people could help you choose the right time !