Spectacles holder for the sun visor

The printed frames, M4 screws and nuts, few cm of fuel tubing and a tool on table.
I have been trying to find a spectacles holder for sun visor that I could operate with one hand, and that would work both the visor up and down positions. This is a need for us with glass eyes, one would like to swap regular glasses to shaders on the fly, with single hand.

I could locate one commercial option. It was over engineered with a button and springs, it turned out to be quite flimsy and broke after a few weeks of use. Thus it was not an option. I needed to design my own.

I did few designs through trial and error, this is the third iteration of the plan. I designed it for M4 screws and may later swap those to longer ones for the holder to give slightly wider support for my glasses.

On the picture right you can see the installation going on.

The black rubbers on those screws are old fuel lines I had lying around in my garage. They are there for looks, and to provide little spring tension for the nuts. Not really a functional part, that is.
At first dry trials this design seems to work ok. On picture right you can see my regular glasses hanging in there.

The holder will not fit Mazda MX-5 as the sun visors on that car are different in shape. But this will fit both Abarth and Fiat 124 Spider 2017 and later.

The 3D printable .stl file is in this zip file: Fiat-124-Spider-Sunglasholder.zip