I doubt that would be too short, it's all a matter of what look you like. I actually cut mine from 500mm(19 5/8") down to 300mm(11 7/8") just because I just rounded off the # to 300, no peticular reason. I doubt 3 more inches would make that much difference except maybe a little louder, which mine increased loudness probably by 50% than original. And as far as having to re-jet , I haven't any need to. I have only ridden it a couple times since the mod, but actually it seems to breathe a lot easier and throttle response is more crisp. Here is the link to my mod with pics.

https://www.superhawkforum.com/forum...ad.php?t=17038