Show me your side exits

I agree. The x should balance the sound so you get all eight pulses on each side.
What mufflers are you planning?
I have a theory of how to get a quiet, good performing exhaust. Pick out which type of muffler has the sound you like (triple pass, straight thru or Flowmaster style) get the right size thru pipe for the application, and use the biggest longest muffler that will fit under the car.
Thinking of going with dynomax race bullets