One thing that concerns me is having the two braces going into a 6 inch post. If you have housings, you won't have much of a tenon on your braces. I would go with 7"x7" posts.
You don't say what dimensions the shed is, 12'x20' maybe? Also, what length timbers do you have available for the top plate. That will determine how you splice the two pieces together, which would ideally be over a brace.
