Just to add something to post #5 by BackPacker, have a quick look at some of the videos put up by this guy...he uses cameras in various positions, has pretty darn good audio and generally makes the whole trip very interesting. He seems to be very approachable and I'm sure he would give you some very helpful advice, based on his experiences.
https://www.youtube.com/watch?v=BEF4C25UI6Q
Hope this helps you.