I bought a Runcam 5 Orange yesterday and took my first ride with it. For a lot of reasons this seemed to be the one to get: low price, high quality, compact, and users flying it on drones say it's indestructible. But it's not waterproof. I think I can fix that.
For the trial I taped it to my front rack with gaffer tape, pointed level (that's relatively low) and back 45 degrees. It covered straight back along the side of my bike (including one pumping leg) right up to 90 degrees to the bike, so anything coming from behind on my left is covered until it's half past me. The stabilization worked perfectly, and resolution is high enough that I can easily read the plates of passing cars. The quality is actually amazing. I'll upload a video, but I understand that YouTube messes with quality, and it is not the quality that I see on my computer. Click the little gear on the control bar to see it in their best degraded quality.
For an easier permanent installation I'm experimenting with strips of an inner tube taped to the rack with a space to jam the camera in. Not riding, it seems totally secure. We'll find out for real later today. Another camera for the front and everything would be covered.
I'm still messing with the various settings . . .