Model originally uploaded to Thingiverse at https://www.thingiverse.com/thing:2960222.
I highly recommend you print this in ABS. On my black dash in the sun, it gets hot enough that PETG starts to sag and warp.
This is a dash mount I designed to go with a phone holder I designed for Autocross events.
Holes are patterned for a ProClip ball mount.
I have attached it to the dash using some of the 30lb Double-sided 3M tape to make sure it will not go anywhere.
link: https://smile.amazon.com/3M-Scotch-Extreme-Mounting-60-Inch/dp/B005SRECEU/
I have uploaded the latest version, This one has been in my car for 4 or 5 months now with no issues. The fit is good and I have been using it to mount my OnePlus 6 phone on the dash at Autocross events and just everyday driving.