I printed Attempt5 and, whilst that sharp edge adjacent to Finger5 got in the way, it was determined that a solution... may exist. 

🎊🎊🎊

Attempt6

I noticed that a more acute angle may improve screen visibility, so I tried an 84 degree angle:

As you can also see, stylistic choices like a section of logo bracket and filleted chamfers have made an appearance to obtain a solution that didn't look incredibly disjointed or overly sharp.

I printed that and my takeaways were:

• Finger5 does not fail the solution.
  • wohoo
• The 84 degree screen angle fails the solution.
  • sigh
  • The whole thing just feels crampt and the bottom of the screen started colliding with things like my legs or work surface.
• The ergonomics of Finger5 (and the other ones, to a lesser extent) is dependant on the arm's angle.
  • So I was onto something with that screen angle idea, at least. Unfortunately, moving that angle to the Tetrinsics is unlikely to work, since the ends closest to the screen would increase in Z height (relative to top of arm).
• The draft angle when used on a work surface could be increased to give Finger5 more space, and there needs to be more worksurface support at the end corner.

Attempt7

Attempt6 showed promise, so I:

• Increased the main draft angle from 8 to 9 degrees (which increases the longest length to 95.7mm)/
• Returned to a 90 degree screen angle.
• Moved the "bracket bend" so that it was 2mm away from the edge of the milky-green section (2mm is the offset from the white L to the milky-green section).
• Move the strap back to centered-to-screen.

Attempt 7.1

I printed 7 overnight and it turns out Fusion360 threw one of the strap holes somewhere, so I couldn't mount the strap.

The increased draft angle worked, but I thought that the angled face that the thumb pressed on was too high, so I reduced it such that both sides looked more symmetrical.

I accidentally tried Attempt5 on the wrong arm, and it felt more comfortable than Attempt4 and its centered-to-sceren strap location, so I'm now going to try centered-to-back:

I've also increased the height of where the front strap starts.

I'm also going to try keeping this face parallel to the belt so that the top face doesn't look all misaligned. If you look at the Attempt6 prerender, you'd see that it angles away.

[20 minutes later, whilst setting up the render]

Just did an offset on the face to fix this fillet that has been annoying me. Restarting the print now.

Comparing Concept1 Attempt[latest] to Concept2 Attempt7.1 

Shakes head in disgust and disappointment.

All the sacrifices I made, all because I said / thought:

• 60x60mm height and width MAX.
• Finger5 would just get in the way, complicate the design and thus should be avoided.

Both designs have a 9mm thickness behind the screen, similar thicknesses under the Tetrinsics (20 vs 20.4mm) and similar max lengths (91.7 vs 93.9mm), yet Attempt7.1 looks sleeker, thanks to its more modern looking design. The fact that A7.1 is 80mm at its shortest length also helps. Because of the strap, even the 70x70mm Attempt7.1 doesn't fully cover the top of my wrist, so Concept1 likely would've had issues with thumb reachability anyway.

Unlike Concept1, C2 A7.1 can be taken off and used on a flat surface. It's also got a larger, higher PPI and refresh rate screen with thinner bezels now. 

Admittedly, this entire run was sponsored by #Tetent TestCut. Thank you Me In The Past 😭!

Attempt7.1 renders