Hi Claude,

The best combination is to soft mount the engine and use a tuned pipe. The sound is similar to a well tuned OS140RX or slightly better. Not as quiet as an electric but in the air, it's in similar territory

The pipes I have used and recommend are the ESComposites 30G or 40G and the the Mintor 38cc pipe. They are very lightweight and put out much better torque on larger props. I have never used a muffler or canister so I can't give any suggestions there. But I think that you will get something from a soft mount. The soft mount that's best is the Hyde style rubber isolator. I make my own custom mounts and nose rings that are based on Merle's design

Edit there is just enough space on the crankcase around the front bearing to design and install a nose ring. My nose rings for gassies have a recess for the Hall sensor such that the sensor doesn't touch anywhere. Clearance is small on the order of 1/2 mm on top and 4mm on either side. The front of the nose ring is flared out suchthat the prop drive washer doesn't touch. I usually chamfer the aluminum drive washer's tail end to eliminate any possibility of touching. It takes careful planning and carving to get a ring to work right, but the final result is much better flying set-up