I put a Delkevic 14" shorty on my '15 model a couple of thousand miles ago. It's a bit louder than I expected so if this is one of the quieter options, I'm glad I didn't try anything else. I have not bothered to try it with the silencer /db reducer removed. So far I like the sound a lot, it's got a nice growl on throttle overrun and no annoying popping at all. Hanging it with the included hanger bar ensures the exit does not fry the turn signal or reflector. No problems at all with that. At first I didn't like the lower angle when mounted but now I think it looks good. I was thinking of cutting back the OEM shield but I kinda like how it looks as is.
A note if you have the OEM side cases, the 18" models will tend to interfere with the left bag because the pipe will be longer than the recess in the bag that's meant to accommodate the OEM pipe. It's tricky to get the longer pipe not to touch the metal shielded part of the left bag. I you have aftermarket luggage, that's less close fitting than the OEMs, or no luggage, fitment should not be an issue for the 18".