If I was you, the first thing (and I DO MEAN FIRST) I would have done is measure the room? Yeah, that makes sense to me. 20 1,000 watt lights IMHO will be too much for your room, though like you said, you haven't measured it yet. Way to go, stick your neck out there talking about a 20 light 400 plant grow that is going to happen, when you don't even know that it will fit!? Anyway, I am not being rude buddy, I (and president teddy roosevelt) am just saying this :

Speak softly, and carry a big [weed] stick, you will go far.

I mean - tell no one, and be ready to do "battle" when the time comes. By battle, I mean arm yourself with knowledge of your local laws regarding plant numbers, as well as any other information you can get your hands on. Obviously, please don't go outside and actually get a tree branch to hit someone with, but be aware of the dangers out there. Good luck bro (or bra), and peace!!

PS - I wanna see pictures of 400 plants being harvested ha! My hands are hurting thinking about all the trimming that would be involved.........:jointsmile: