If beerfreak's posts are planed timbers then the layout and cutting of the braces in the center of the posts will work, as he can measure the mortise depth and housing depth (if he's using one) off the surface. But if his timbers are rough sawn then centering brace mortises and housings in the post are difficult to measure and cut accurately.
And brace layout accuracy is important for the brace to truly work as it should to prevent racking of the frame caused by the wind.
I agree with NH's comments about off center tenons and the possibility of the post being twisted.
One solution would be to also center the post top tenon to whatever he is using for a plate.
Being an open car port he will have to be concerned about wind up lift and the posts will have to be properly secured to the foundation to prevent any movement due to up lift...
Jim Rogers

Whatever you do, have fun doing it!