Here's the STL:
https://www.thingiverse.com/thing:2357452/files
I'm not good at modifying STL's so in Cura I changed the width to 100mm and the height to 70mm.
Then I mounted this ball mount to it:
https://www.amazon.com/dp/B009AYLYWA?psc=1&ref=ppx_yo2ov_dt_b_product_details
Ball mount is mounted so its flush with the top of the angled bracket. I'll take a picture today after work.
I ordered the vent mount plate but from what I understand either would work for this purpose (since the plate itself is the same for both and I’m not using the mount portion).
I ordered this ball mount plate if that’s what you meant
I’ve had mostly the same experience but I haven’t had to do anything to make it happen—it seems to center itself pretty well as far as I can tell.
As promised, here are three pictures
The wireless charger is made by Owl (LINK). Their website is disaster. Don't feel bad if it takes you forever to figure out which model you want, lol
The charger came with suction cup and vent mounts, but it uses a pretty standard 17mm ball socket. I used a mounting base I had laying around from a previous car dock that matched the AMPS mounting pattern. Something like THIS should work fine.
I've had this setup for about 2 years now (it was in my '12 WRX too), and other than a little bit of vibration on the highway, I'm happy with it. Nice to not have to plug in the charger every time. :)
Note that the wireless charging current is less than plugging it in, and the nature of wireless produces some heat. If I run an app like Waze which keeps the screen on, the wireless charger won't keep up with the power drain, and the phone also overheats after a while. On longer trips, I just plug it in instead.
EDIT: Found the mounting base I used, but it's discontinued :(