Hello, here is a link to the iPad mini 4 dash mount I created and uploaded to Thingiverse. If you have a 3D printer, you can download the files and print your own. It takes about 20 hours to print all the parts. My model 2015 model S with QC has the non-navigation radio. The USB jack does not supply enough power to keep the iPad charged. So I use a high-current power adapter instead and feed audio to the head unit through the AUX input. Using AUX instead of the USB input, you lose the display of the song info on the head unit, which is shown on the iPad, so no loss. You also lose the ability to change tracks with the steering wheel control, which in my experience works only some of the time.
I have found that my WiFi/LTE iPad mini is so much better than even the best head unit replacement. I toyed with the idea of getting one of the wireless CarPlay head units, but they're incredibly expensive, and CarPlay has such a limited number of apps you can use. With the iPad, you can have 2 apps running at once side-by-side. I have mine set up to show Waze on the left and Apple Music on the right. And a nice full-screen LeafSpy Pro is awesome to have and will be even more awesome once the developer updates it for use with split screens.
Anyway, as soon as it's printed and installed, I'll upload some pictures. I'm a new 3D designer, and it took a few days of work to model it.
Here is the link: