Love the design. If you're worried about seals between panels, you could use silicone sealer and 24 hours later you have a good smooth seal.
As far as air movement, I don't forsee any problems. the direction of change in airflow is conterbalanced by the sheer volume of airpace in the turns.
It looks like you built this box for a specific spot in your car. If you dont' mind, i'd like to see where you plan to put it. Several of my buddies on the corvette forum have been thinking about ported boxes for the center cargo compartments on their C5's.
looks good so far.