Well, I have ordered a simple baffle that will be held in the silencer tailpipe by a single bolt. It will be interesting to see what effect it has.
Nothing is ever simple of course, the nearest baffle diameter I found was 35mm - but the ID of the tailpipe is 37.65mm (1.482 inches - presumably 1.5 inches without the carbon

).
I'll try to 'expand' the baffle sleeve under the hydraulic press and if that doesn't work I'll make a cylindrical spacer and press the lot together.
I have a spare 32mm concentric that I bought back in the 1960s (when converting my 350 AJS to 500cc

). It has a brass fuel metering jet for the idle whereas nowadays there is just a drilling in the body - food for thought.
Life, of course, has got in the way of my 28mm carb strip-down. Yesterday was 'Fathers' Day (

), daughter & family came over, then their car broke down on the way home (who thought that putting the electric fuel pump inside the fuel tank was a good idea !) so I have lost my Ford Focus. Today I have peace so I'll get on with it . . but the grass needs cutting . . in fact I could do with a Silage Cutter its so long . . Hey Ho.
No wonder Classic Bike Fettling takes so long.
Bob.
My avatar shows the late Len Rich in 1970 with the bike I now have - a 1958 Ariel VH