Thanks everyone for your replies. Here are the chainplates that will eventually go back on the boat. Lacking any information on a "proper" angle for the "mids", I had them flattened and will do more research on the angles and pay close attention when I reinstall them on the boat.
I still like the external chainplate idea/look, but with a set of good ones on hand already, and assurances from the boatyard manager and fabricator that they are all sound, it seems to make more sense to go with the original setup.
I'm in the process of tracking down previous owners to see if someone had rerigged at some point, because, as you see, the "originals" are stainless, not bronze. I would think if someone HAD rerigged the boat, that the Backstay Chainplate would/should have certainly been replaced at that time, but since it obviously wasn't...
Anyway, I tried to take this picture showing the angles they are bent. They are laid out from forward to aft, port and starboard, just as they'll be replaced on the boat. Only the aft chainplates have a bend now.