My wire securing method matches Pat's words pretty closely. Secure everything but not so tight that the wire ties and/or wood cuts into the wires. Securing something too tight can actually transfer vibrations better than if you left it a little looser (ie velcro squeezing down an ignition module's foam padding against the motor box). Moderation is good. I never leave anything over a few inches without being secured. G forces will tug on the 2 ounce extension and make it a pound during a snap roll. And always go over the plane now and then to look for cut wire insulation and fuel lines. This is one of those "ask me how I know" experiences. The sharp edges of thin ply makes great gas engine powered mini saws.[X(]

Is it just the picture or is your muffler almost touching the cowling on the right side bottom?

PS Edit: And every time out, as a pre-check, always push down on your rx's servo/battery extension plugs to make sure they are bottomed in the sockets.