...unts/roll-bar-mount). In this case no coupler is needed and the camera is very close to the front tube to minimize vibration. I use a lanyard on this as a safety precautio...
My carriage keel has a square aluminum tube that is flat on the bottom and I use a standard flat adhesive GoPro mount for this. I use a lanyard here also as described above. You can see some video taken from the bottom at this link: http://www.youtube.com/watch?v=voQGcLjnEPU