[Chili Palmer]

I've bought a pair of M6 mufflers for my 650 GC that I'll be installing with a one piece carbon fiber diffuser to replace the existing one on my car. How big of tips can I fit on the M6 mufflers?
I've seen some direct billet replacements that are 3.75" wide, I also see a lot 4.0" carbon fiber Akrapovic copies that would look good, but is there enough spacing between the muffler outlets and will they sit back far enough not to stick out past the top edge of the diffuser?

Thanks in advance.
CP