Up to this point I've just been using the camera mounted on the Invisible Selfie Stick and holding it while riding. One side benefit of this is that it makes you a lot better at riding one-handed.
I have the Venture case and the extended selfie stick on order and perhaps, when the case comes in, I'll feel a bit more confident about attempting to mount the camera. Right now I'm paranoid about it somehow falling off and damaging the lenses.
Have you seen what Insta360 call "The Back Bar"? That seems like a good solution.