I used the stock Saito muffler with an exaust extention running out the bottom of the cowling. The engine is mounted on its side to allow for the exaust to exit the bottom.

I have however, had problems with the end of the muffler comming loose and loosing back pressure on the engine. I have since had the muffler end welded and should never have any problems again.

Anyway, hope you enjoy your new plane and let me know how she flies.

John