My advice is to stay away

My advice is to stay away from corners due to potential shadow problems. If you insist doing it this way, try to round the corner off in some way so that it’s more like a U instead of a right angle.
For inspiration, take a look at this studio shot.
http://3.bp.blogspot.com/-8u3mj9pF0sQ/UfEiSdmpxHI/AAAAAAAAAMQ/Pj2eLlkOM9Q/s1600/Cyc+Wall+at+Westlight+Studios+facing+northwest.jpg.

Mike