I loved the original design for a mechanical phone holder, but my car vents don't work well for holding phones and I live in a colder climate so my vents often are blowing hot air, which isn't good for phones.
I added a GoPro mount to be back of the back plate, which removes the slot for the vent clip. I then designed a customizable CD tray GoPro mount in OpenSCAD.
I've confirmed this one fits in the CD tray for a 2005-2011 Honda Civic
Amazon Basics PETG
Since this will be in a car, I recommend using PETG or ABS. The back plate will require supports on the build plate only and should be printed with the GoPro mount down. I also used a support blocker under the center slot for the back plate, to make support removal easier. The sled will also need supports. I printed it with the back side flat on the print bed and supports under the raised part. Nothing else should require supports.
Most parts should require minimal infill (5-15%), but you should print the arms with higher infill to increase their weight (80-100%)