I personally wouldn't fly a Robbie in mountains, time and time again we see this accident. It is obvious to me that when a Robbie is flown in mountainous terrain and it lands where it intended then the pilot got away with it and they didnt know how close to the edge they were. So they will do it again.
Its the wrong tool for the job, use a heli not susceptible to mast bumping if you want to fly over high hills or mountains.
No disrespect to people involved.