I bought a dashcam while on holiday for use in my Toyota Avensis 2005. It came with a suction mount that I didn't trust, plus this solution blocked too much of the view. Also I didn't want to see the LCD on the camera back side as I was driving, it could only be switched off after 3 minutes.
The solution was to mount it behind (as seen from driver) the rear view mirror. It is more secure, does not block the view and hides the LCD.
The adapter is custom for the car and camera, made with my AngelCAD software.
Edit Aug 4, 2017
This is the camera
Mark 2 version of the adapter is uploaded, more compact.
0.3 mm extrusion/layers
The printer is a Simple Metal bought 2015 (not "play")
Made cardboard sketches of the mirror profile(s). Scanned the sketches and converted them to 2d profiles using AngelCAD. Extruded them to 2 flat holders, subtracted a mock camera tilted 15 degrees to make holes in the holders. Connected the holders with a cylinder attached with 2 screws.