That particular sample of a two-rivet d-ring certainly wouldn’t work. In the available reference images, the clip seems to run parallel to the loop that holds the ring, with the edge curved so as to hug the bottom lip of the flash tube.. Basically, Roy’s setup, but with two rivets instead of one. A long strip of metal with rounded ends that was looped back on itself and riveted to the endcap.
I’m subscribing more and more to the handmade bracket theory. Maybe the Elstree prop really IS a Rosetta Stone for the onscreen hero(es). The only likely difference is that the hero bracket seems longer, and thus more centered on the endcap.
I’ve been trying to scratch my ANH Graflex itch for nearly 20 years, beginning with my old Larbel, then the Master Replicas Elite Edition, then the Signature Edition, and now my new TGS. Although I fear the itch won’t truly be scratched until I go full vintage.
Of course, when the Force opens a window, it closes a door. Just when we might actually have solved the last key mystery of this iconic prop, those friggin’ mystery fasteners are discovered between the grips. Un-friggin’-believable!