I decided my PEAK loupe wasn't quite up to the task of composing in bright light and I needed a full groundglass loupe.
With very few ~6x7cm loupes out there I decided to take a leaf out of the book of many an internet photography hacker and took the rear cell out of an otherwise junked lens.
To my pleasant surprise the focal length when coupled with my eye is about 85mm.
After a couple of quick prototypes I have this:
I need to make a neat way of attaching it other than strong rubber bands. I'll probably make a system that clips onto the groundglass somehow.
The corner indents indicate to me the limits to the stitched image in vertical and horizontal orientation with my chip (37x85mm and 49x73mm) on my STC.
Distortion is vastly less with my eye than through my P&S.
I thought it would be worth sharing with you guys.