GPJ: With a tuned pipe on that .45 I think you may be overdoing it. I would fly it just on a muffler. Also,if you were to sling the pipe under the fuse,attachment & ground clearance might be a problem.
Remember this is not a high speed demon. It is meant for 3D which is generally a slower type of flying.
In any event,be careful at high speed with those big control surfaces,you would not want to bring on a dose of flutter.

Good luck,,,,,,,,,,Dave