It also makes for a little cleaner install without the muffler hanging out the side. I think it also takes a lot stress of the head since the pipe is mounted and most 4-stroke mufflers just hang there. Even if you decide to go with just a muffler, I would seriously considering using header and more of a Pitts Style muffler you can get from Central just to clean up the install.

No matter what choice you decide though, I would definitely recommend soft mounting the engine just to take stress off the airframe.

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