This classic image is pretty darn close to being a plan view of the prop, and it indicates that the d-ring bracket was virtually on-center, since the rounded section section of the bracket which retains the ring lines up with the space between two grips and the rectangular holes on the clamp band.
I think it’s very safe to say that the Elstree prop is definitely not the one used in any of the publicity photos. If it is indeed authentic, then it would most likely have been a backup/second-tier hero or a failed FX attempt.
In terms of impacting what we know about the onscreen heroes, the only real question is how the d-ring brackets were attached. If the heroes indeed used a found part for the d-ring brackets, then I’d be inclined to stick with the one-rivet notion. The Elstree may actually line up more closely with the Vader Barbican (now thought to be an ANH FX stunt), which also used two rivets to attach its d-ring. Perhaps the two rivets were used BECAUSE it was going to be a stunt, and therefore needed to be a bit more durable.