For a deck paint a few years ago, I removed every piece of hardware and all trim, so it was a good opportunity to add backing plates ('76 E27). I know not all boats of the same model are identical, but be prepared to make some access holes for some of the hardware since it becomes evident quickly that most of those items were attached to the deck before bonding to the hull during manufacture. As a result, accessibility is sometimes limited and some nuts and washers can be buried in glass where having three arms would be useful.
In addition to the plates, I had to make angled spacers for some of the stanchion base fasteners because the angle of the deck and the underside are not the same, so the original fasteners were forced to bend. The new spacers kept the nut and washer perpendicular to the fastener.
Another problem area was where a couple fasteners lined up with bulkheads and the production solution was to drive in some plastic expansion anchors. I had to do some work get access and then to cosmetically cover a stronger through-bolt system. This was on the stanchion bases where lines are readily attached, so I considered strength to be important there.
I bonded the backing plates to the fiberglass so they became part of the structure and do not become a loose part when removing or mounting the hardware. Not sure whether this is standard procedure, but seems to have worked out OK.