I sort of explanied the way I made the pannier mounts for the motosport pannier frames a few times - I talked about it earlier in this thread didn't I
I am a staintune can fan and have ridden a bike with Triumph off road pipes. I have heard the Kiwi pipes too. I sounds smart arse but I think I made the right decision. They are awesome (poor word choice). Quiet noise at idle, start it up with a bit of juice and it emits a shotgun crack (I scared the bejeezuz out of old guy one day) the sound builds a la ducharleyessque and then for a while they sound like an offenhauser speedway engine ...I could go on but Ill spare yaz.
I like assertive sounding bikes, not necessarily loud ones so I keep the end caps in, I have elderly neighbours.