Off topic. Do you know the part number for the K & N Air Filter for the R18? I can't seem to find it.Not sure if that can be done without a cutting tool and re-welding the area that holds the baffle/end caps in place.If you take off the end caps you will see where the baffle is welded.The dealer told me that one of their customers did cut the welds but could not reinstall the slash end caps.This is because the baffle is connected to the muffler body that attaches the J clips to allow the end caps to be attached.
Also, to add a note here.It does look like the center plug could be drilled out but,the oem mufflers cost over $1300 each to replace.
Sorry I cam't be of more help.
I am not willing to do a $2600 muffler experiment and have the bike sound like a motorboat.Freedom Performance has slip-on mufflers that look pretty cool with end cap options for the R18C.
I did a K&N air filter(left off the puny intake tubes) and a BT Moto tune.The bike sounds deeper and throaty with increased power.The mufflers do break with riding.I'm at 12,000 miles now and kinda like the sound. I have a sidecar and really don't want it to be louder than my 2 wheeler.
Good luck.I am interested on how your research turns out.Glad for your post as that is what this forum should be about.