I have this plane, I mounted a YS63 inverted; I got a 75 degree exhaust elbow and matching muffler; not sure from where; the Muffler exits straight down out the bottom; the angle of the exhaust port allows this 75 degree elbow to make the muffler hang straight down at 90 degrees; several elbows at different degrees are offered from this retailer; it's possible the thread is the same as Saito's; if you check the other Decathlon forums the retailer is listed in the discussion threads.