Marty, I was lucky enough to purchase two Blueheads last year, one slightly used and one NIB. The used one came with the muffler that is currently used by the ST .61 and it fits the Bluehead. No, it won't have the "ring-a-ding-ding" sound when you let off of it (don't you just love it!) that the old stock mufflers and the Semco mufflers had but they are a helluva lot quieter than the open faced mufflers! The Mac's one piece muffler sounds like a great idea and that's what I'll probably go with. My Southern R/C Tigertail will be built this year! With Southern R/C tri-gear retracts, of course!
Frank