1. Re-inforce frame (if needed) to support heavy lights, etc. 2. Line the inside with your favorite "Light proof / Reflective" surface, or paint. 3. Make any, appropriate, holes for ventilation / ducting, etc.
Two of these puppies can be attached (back-to-back) with a re-inforcing strip joining the two. Then just cut the backs out and voila, you have a DoubleWide! If you make a "Double", I highly recommend bracing the "missing wall area" with a big "X" made of guy wires for support!