I just put it on the trim under the steering wheel column. Used double sided tape.I successfully installed the ISUDAR system in my '16 Turbo yesterday. I had to make a trip to the hardware store since the included standoffs didn't leave enough clearance for my Sirius module but that was the only surprise.
I'll agree that audio quality is much better when using AUX BT, but then you lose Siri and navigation audio so I'll probably just stick with AUX for the most part.
Thanks to everybody in this thread for the information. @Santirx maybe I missed it but where did you mount your microphone? I tried getting into the overhead console but was afraid of breaking something so I just stashed the mic at the top of the A pillar for the moment.