I've designed and printed 2 concepts. The first one was a general shape and the second one (pictured above) was moving the Finger5-to-Finger4 offset from 26mm to 21mm, adding a screen I just found and changing the back angle slope for better ergonomics.

First version:

The LPM013M126 screen I found:

This screen is rather nice because it's reflective and backlit and doesn't cost £50. I was going to try and use a 21700 when I reduced the Tetrinsic offset, but this screen would only barely fit with the 26650.

The second attempt:

The sceen is on the most ergonomic face, so I'm thinking of skipping the 2.7" screen either altogether or until I've got a working prototype and feel that I could use a larger screen.

I'm also thinking of designing the rear-hand mount such that a pocket (shown in purple) could slide inbetween the hand (brown) and the TimerSpy (grey):

That way, it shouldn't get in the way when putting my hands in pockets while still being able to slide through a sleeve.