Obviouslly i wouldn't let the brushless motor in the nose without a dummy engine covering it...
Once again, coming from the 3D project to the real world i casted some polyester resin inside a tube and used it to machine the cylinders and the engine body.
The dummy motor will be splited in two parts.
The back part (backplate) will be used to mount the brushless motor and also will be screwed to the firewall, then, the front part of the dummy engine will cover it all and be kept in place just by press fit on the back plate.