I hate to see someone loose an engine. There is an easy way to ensure you keep an engine in a crash. I wrap a steel leader around the engine securely, then attach about fifty feet of strong fishing line to that. I attach the other end to a bobber and coil the whole thing up in the plane. You can also attach the other end of the line to a solid point on the plane, so the plane itself becomes the bobber. Either way, if you do crash your plane, you can just find the bobber and pull the engine back up. BTW, I'm not taking credit for this idea, I'm just passing it on.