I also fly the Rossi 45 rear exhaust Powerhouse from Morris and you are right about the noise. My muffler snaps on over a elastomer o-ring. I believe a replacement is not possible unless you make one yourself from a Rossi connection. I fly the ENYA 50CX, Webra 50 Speed, MVVS 49, and this Rossi and our field operations person said they are all to noisey. All have baffle-less mufflers.