I have the same plane with OS46FX. I used a Slimeline Pitts Muffler. It worked out very well. I have about 40 flights on her now. I did have to use longer servo arms on the aileron servos to prevent the clevis' and control rods from hitting the wing. If you do this, make sure you limit your EPA. I mixed some expo in on aileron and elevator about 10% on low and 20% on high rates. Used throws recommended on all surfaces except the rudder. I had to increase the rudder throw to get it to knife edge. The plane is fairly fast. Clocked it at 80 MPH two weeks ago with a radar gun at full throttle and in a dive. Got a little whistle but no flutter. I originally had the wheel pants on it but then removed them and installed larger wheels because I fly from a grass field. Probably would have got 85 MPH with the wheel pants but takeoffs were getting hairy with the pants on. Good luck with it!