Here's a pretty well-edited video.
Nothing fancy about the mounts, but the variety of camera angles makes it a visually appealing video.
DVD-length videos are a PAIN, but 3-5min YouTube/music video-length videos are absolutely do-able with 2-3 hours of good raw footage.
Edit for "feel good"/"visually appealing" as opposed to trying to edit to tell the story of your entire day on the river.
Say you shoot half the river with the GoPro mounted to your raft, the other half mounted to your helmet. Edit it so you view a video with raft/helmet/raft/raft/helmet/helmet/raft (etc.) views of rapids. Only people who really, really know the river you're on will notice that you are showing your video out of sequence.
Clips of people doing silly things at the put-in, scouting the rapids, candids at lunch or the take-out are also good to add in. How about a bocce ball game on a sandy beach at lunch time with the GoPro buried in the sand near the object ball? Get creative and get footage with editing in mind--you need to edit a video or two to know what you'll want--and then your video capture and camera angles can be more "intentional".