With a Scrog you want it at least two feet high right?

I would take 1" by 2" Frame out the top and then lay the screen on top and just bang another one by two over the screen. As far as legs depending on space you probably could use the 1'By2"s Or just mount to the walls if you can catch two sides.... I seen a god thread with Scrog grows and the guy said to be sure to get the plants under before they grow to big... Very important he had issues with a few from that.