Lowell - First I want to thank you for your contributions to our forum and sharing your experiences and knowledge. And that goes for everyone else on our forum. I studied your picture of your iPad mount on the underside of your panel. Very creative. I'm going to try your version and see how I like it.
These are photos of my current solution and this works for me. After watching Trent's videos, I heard him mention he uses the inexpensive "Smallrig" clamps, so I bought a couple. It's a good bargain and very reliable.
I 3D printed a back plate and mounted it to an inexpensive ($5) iPad mini case and attached the Smallrig clamp. It can be mounted to any cross member tube in the cockpit. I also 3D printed a similar case for my phone.