Very similar to my first setup. I used a 150W HPS and 70W MH (dual spectrum rules FTW!) metal should work fine, although be a little tougher to cut the holes for ventilation - Is the inside painted white? I got it to average about 200G from 2 plants every ~ 65 days. Separate chamber for cloning/veg so it was always running. Once you know how the plants grow you'll be able to maximize the space. Heat was an issue at first, but a 140cfm bathroom fart fan cut into the side of the cab fixed that