It's Dynamite. Local muffler chaps did a superlative job, I am well chuffed, $100 AUD, (70 USD) Which is what the Ryca exhaust adapter would cost me delivered to Australia!
Sounds freaking awesome, much much better than I expected. I installed a 150 main jet and as the plastic washer was only 2.5mm thick instead of filing it down, I moved the clip position one notch down because the notches are only 1mm apart so moving it one notch down was like taking 40% off the thickness of the washer. Maybe the US spacers are thicker, I've heard they are 5mm.
I also found the plastic tube in the diaphragm spring like IslandRoad, so I turfed that.
Haven't had a chance to take it for a big ride yet, will go out tomorrow, but so far it seems pretty good. Could be a bit of a problem with speeding fines because it's difficult not to crack it open it sounds so good.
The old muffler sounded like my Bernina 730 Record sewing machine, which is good for a sewing machine but nicht so gut for a motor sickle. Now it actually sounds like the genuine article.