Ed,
It is not only a Super Tigre muffler "problem"...
...OS engines and all their South-East Asian clones use the same metric threads that ST, Webra, MVVS, MDS, Moki, Rossi and many other 'rare' engines use...
It is that, or sticking with K&B and with Fox (Fitzpatrick?) engines that have Imperial threads.
It looks like you will have your PITA and have to eat it too... I recommend some humus and falafel balls
