Making a bike quieter?? Who'd have thought anyone would ever want to do that!

My MC21 (Johnnymac's old bike: http://www.nsr250.net/forums/viewtopic.php?t=13442) has MMAX pipes, and they have consistently tested at 102.6db. At Brands the limit is usually 102db so it's not ideal. I have re-packed the silencers but no real change.

One expensive option is to buy another set of pipes, but might this will need the jetting to be altered?

Or could I make slightly longer and/or fatter silencers? I don't know if the internal pipe diameter (approx 1") plays a large role here than the silencer volume. I have the facilities to knock a pair up.

Any suggestions gladly welcomed!