Oh!
Thanks very much for the photo, Peter; this really shows the map case fully realized. You may not have "invented" it, but your execution is very well done, and this will help a lot of people, I am sure.
In some applications, I can see it working i tandem with a handlebar bag map carrier to give a "double-tall" view with two maps displayed at once, much as when a person unsnaps and fully opens the Ortlieb map case. Or...an guidebook opened to a detailed view in one map case, and an overview map in the other.
It surely looks good!
All the best,
Dan.