I got the Secret Jardin's Dark Street 150, I got 600w in there I want to add 600 more. (2x600=1200W) My biggest fear is the weight they're going to put on the tent and I'm scared it'll crash it or something. I will take care of the heating problem, I'm keeping it closed to the window and cold air goes in from the vent.
How big is that tent? One thing you can do, that I did in my tent, is build a simple frame inside the tent of 2x4s. I did this so the only thing the metal tent poles are doing is holding up the tent. All my ventilation and lights are hung from the 2x4s. Much sturdier.