This is version 2 of my GoPro Bicycle Seat Mount. The camera will face backwards. Fits on two seat rails, which 42 - 50 mm apart. You can adjust dimensions in Fusion 360 to make it fit your bike, f3d file included.
Use 3+ outer shells (Perimeters)
3 top and 3 bottom layers.
You will need 2 M5 Hex Dome Cap Nuts And 2 M5 Socket Head Bolts.