My hypothesis remains that the propmakers were reinforcing the D-ring attachment in some way. That the placement is right next to the d-ring rivets just reinforces my suspicions. Given that we know they had at least one other 3-cell bottom without rivets/holes in the sides, it just doesn't make sense that these would end up on the hero unless they were supposed to be there.
Ohhh, I’m gonna have to re read that post now!