I think if I had to do it all over again I would've started with modding the oem mufflers e.g.
https://www.zpost.com/forums/showthread.php?t=1398616
Seems like you'd get some of the bass cancellation of the oem mufflers and more high-frequency scream at high RPM. The oem muffler design seems pretty high-flow. Perhaps even more so than powerloops since the powerloops have a couple of 180 degree turns.