Sorry I was to suppose to post this the other day but I've been kinda busy but here ya go
I've been asked several times on how I made my inside structure. I used a plywood base that I got out of the scrap bin that just happened to be the perfect size. I drilled four holes in the corners the size of my 3/8 all thread bars.
From the bottom up it goes
Nut/washer/plywood/washer/nut
For the scrog screen I used four wooden planks almost the same way and drilled out my holes to fit it over the 4 corner rods
Nut/plank/plank/nut
And for the top light structure I used 4 eye hole screws that just fit over my corner rods but not over my nut
It's pretty simple and straight forward. Just make sure the washers you use for the base are pretty wide but the right size for your bar to go through. Without the washers it'll be pretty easy for a corner to snap off your base.