Sure, heres prototype #2, I used more of a "chambered" crossover where is a greater chance of pulses collect into that one area to blend vs a traditional H-pipe or X-pipe
Ignore the ugly look, the final version will look normal. Unfortunately the space constraints will not allow it to be clamped on, it'll be a weld-on
Prototype #2 picture
You can see the U-bend added underneath the passenger side rear subframe. Its a good length added in a compact manner...almost 22-24", then subtract the length where the inlet/outlet bend occurs, which is almost 8", effective overall added length 14-16" on my system.
I don't know where the shorten distance in the exhaust occurs in the M2c though as compared to the M3/M4, im assuming its just a shorter mid-section?