The cross-flow was for performance only. The cats, obd2 and muffler are for the state.
Based on Cashburn's feedback, crossing pipes is not even an option. So it's a non-issue. Especially since he will be building the car for me.
So my last question then becomes-
Would a normal non-crossed undercar exhaust with cats and a muffler still give more airflow and HP then sidepipes with cats?