Recent discussion on the Petereson Cutter group has suggested that old chainplates might be good enough if not stressed. In my not-so-humble opinion, any boat still sailing with original chainplates, be it F46, KP46 or KP44, should schedule an immediate replacement. Cracks develop from crevice corrosion where it is not possible to see. If the toggling is not good or the fairlead to the shroud or stay is not good, then metal fatigue can shorten the life of the chainplate. If you are feeling doubtful, just look at this photo from Tainui.
In May 2007, while at the Police Dock in San Diego, I replaced all the chainplates on Beatrix (except the bow) with new ones fabricated from 316 Stainless Flat Bar and waterjet cut to shape. The photo gallery tells the story. All design and CAD files are available in the downloads below.