I know that @Col has a dashcam that records front and rear facing views. I don't know which cam it is, so I've tagged Col and I'm sure he'll let you know when he sees this.
I use one of these. Car Mini Windshield Tape Mount Holder for Mobius Action Cam #16 Camera Black New | eBayThanks Col and Dave. Worth looking at. Which mount are you using Col?
I used this mount, which allows the camera to be slid off easily - But would only work in horizontal or slopping glass surface: