Been there, done that. Heavy, heavy sling load in a 206 into a river bed surrounded by sheer cliffs. Steep descent required, and proved to be just too, too much. collective at max power, unable to arrest the descent until the load hit the ground, gently as it turned out - all luck, no judgement. Tasmania, a great place to teach yourself about mountain flying. Many heart stopping moments, was a case of the blind leading the blind.