Model originally uploaded to Thingiverse at https://www.thingiverse.com/thing:4313878.
I designed this because I wanted a chest-mountable GoPro platform so that I could see and use my cellphone while flying my paramotor. In the current form, this platform extends about two-thirds of the way up the back of my Google Pixel 3. I did this so that the fingerprint sensor and camera would still be usable. I also added several holes to the platform to attach a leash/tether in case the base breaks or anything else goes wrong.
To mount the phone, I used 2-inch wide 3M VHB tape to attach an ultra-thin case to this design. This securely mounts the case, and ensures the phone won't fall off in-flight! I have tested this on numerous paramotor flights and it works great.
I have this mounted to a MOLLE chest harness using my other remixed design for a MOLLE GoPro base, and a standard "curved" GoPro mount. It allows me to flip the phone up for protection during takeoff and landing - this reduces the chance of flopping about or shearing off the GoPro mount.