RE: Electric motors in .40 size airplane
The Elapor foam will handle a crash very well. Not quite as bouncy as EPP, but much more resiliant than EPS ( styrofoam), and I would bet it would protect the electroncis better than wood or the plasticor that US Aircore planes use.
2-3 pounds will increase the wing loading of a .40 plane by 40-80%. That is a lot. That plane is going to land very hot and have to fly pretty fast with a pretty wide throttle just to stay in the air.
What is the purpose of this equipment? Have you considered putting into an e-glider?