+1 on the double-barrel brakes.
While I've always liked the GoPro, I've never liked the mounts. Have you thought about wider bars and hanging a GoPro under it? The "hanging" mounts seem to work better in some applications, though I suppose in theory the vibration issues would be the same. They have mini-steadycam setups now, I think, and the software is pretty good.
The last time I helped anyone with bike-mounted video, we put rubber 0-rings between the frame and all the rack mounts, and put a Sony digital video camera (studio style) right on the rear rack, on a rubber mat, with a 650b rear tire, then he did a lot of editing.