Whats the formula for sizing? my room is 16'x 8'x 8'. 2"x 4" stud wall construction with a vapor seal and R-13 insulation. Drywall ceiling with two layers of R-19 6 1/2" insulation. It's built inside a block walled garage. 2800 watts of lighting total. All HID's are open Bat wing reflectors. Veg...